TLDR
Swiss meringue buttercream is fat-based, which means water-based gel colours fight the emulsion rather than blending into it. For deep, dark shades — navy, black, forest green, burgundy — you need an oil-based colouring like Colour Mill Oil Blend. Add more colour than you think you need, then let the buttercream rest overnight before using it. The colour will deepen considerably without you adding a single extra drop. Never use liquid food colouring in SMBC — it will split the buttercream every time.
Why SMBC Is Harder to Colour Than American Buttercream
If you have successfully coloured American buttercream (ABC) and then switched to Swiss meringue buttercream, you have probably noticed that the same gel colours produce muddy, washed-out results at best — and a split, grainy mess at worst.
The reason comes down to fat content and emulsion chemistry.
American buttercream is made mostly from icing sugar with a relatively small amount of butter. It is dense, sweet, and forgiving. The icing sugar base absorbs gel colour readily, and because the consistency is already thick, small amounts of added liquid do not destabilise it.
Swiss meringue buttercream is a different beast. It starts as a cooked egg white meringue, then has large quantities of butter folded through. The final product is an emulsion — fat and water (from the egg whites) held together in a very delicate balance. Butter makes up anywhere from 40% to 60% of the finished weight. That high fat content is what gives SMBC its silky, light texture and less-sweet flavour, but it is also what makes colouring it properly such a challenge.
Standard gel food colours — including most professional-grade gels — are water-based. When you add large quantities of a water-based colourant to a fat-heavy emulsion, you introduce excess water that the buttercream cannot absorb. The result: the emulsion starts to break. You end up with a greasy, separated, or grainy buttercream that is difficult (sometimes impossible) to rescue. To reach a true dark shade like black or navy with water-based gels, you often need so much colour that splitting becomes almost unavoidable.
Why Oil-Based Colours Work So Much Better
The solution is to match the polarity of your colourant to your medium. SMBC is fat-based, so fat-based colouring is the right tool.
Colour Mill Oil Blend was specifically designed for fat-rich applications: Swiss meringue buttercream, Italian meringue buttercream, chocolate, ganache, and cake batters. Unlike conventional gel colours, the Oil Blend formula "loves the fats and oils in your baking" — blending in smoothly without introducing disruptive water content into the emulsion.
Practically, this means:
- No graininess. The colourant disperses evenly through the fat phase rather than pooling or streaking.
- No splitting. You are not adding liquid that fights the emulsion.
- Better colour payoff. Because the colourant integrates with the fat, you need less product to achieve the same depth of shade compared to water-based gels.
- Colour accuracy. Shades stay true rather than shifting as they dilute through a mostly-fat medium.
Colour Mill Oil Blend is an Australian-made product, available at Baking Pleasures in individual 20ml bottles or as sets. For deep, dark shades, the colours you will reach for most often are Black, Navy, Dark Red/Burgundy, and Forest Green — all available individually.
Can You Use Gel Colours in SMBC?
Yes, with caveats. If you are mixing a soft pastel or a mid-tone colour, a concentrated gel like Chefmaster Liqua-Gel or Vivid Gel Colours can work — but keep the quantity small. A few drops for a light blush or pale blue will not introduce enough water to break the emulsion.
The risk comes when you push gel colours into dark territory. To reach black, true red, or deep navy with a water-based gel, you may need 1–2 teaspoons or more per batch. At that volume, the water content is high enough to cause problems. You will notice the buttercream becoming looser, the texture turning slightly grainy, or visible pooling of pigment on the surface.
The practical rule: for anything past a medium tone — any shade where you find yourself adding "just a bit more" for the third or fourth time — switch to oil-based colouring.
How Much Colour Do You Actually Need?
This is where most bakers underestimate. Deep, dark shades in buttercream require significantly more colourant than you expect, especially when starting from a pale yellow base (which is the natural colour of most SMBC made with real butter).
A rough starting guide for Colour Mill Oil Blend per 500g of SMBC:
| Shade | Starting amount |
|---|---|
| Pastel/light | 5–10 drops |
| Mid-tone (dusty pink, sage, sky blue) | 15–25 drops |
| Deep/saturated (burgundy, forest green, cobalt) | 30–50+ drops |
| True black or navy | 50–80+ drops, or mix with black |
These are starting points only. Add the colour in increments of 10 drops, mixing thoroughly between additions. Then — and this is the critical step — stop earlier than you think you need to.
The Overnight Colour Rule
Colour in buttercream continues to develop after you stop mixing. The pigment molecules keep binding to the fat over time, and the shade deepens noticeably — sometimes dramatically — over 8 to 24 hours.
Sugar & Sparrow recommends placing coloured buttercream in an airtight container and allowing the colour to deepen for 24 hours or more before use. Still Busy Baking confirms the same: "let your buttercream rest for a bit (ideally, overnight). This allows the colour to develop and deepen even further."
This single habit will save you from over-colouring. Colour your buttercream the night before you need it, refrigerate it covered, then bring it back to room temperature and re-whip briefly before use. The colour you see after resting will be noticeably richer than what you mixed.
For black specifically: aim for a very dark charcoal the night before. By the next day, it will be true black.
How to Avoid Splitting Your SMBC When Colouring
Splitting is the most common colouring disaster with SMBC, and it almost always comes from one of three causes:
1. Too much water-based colourant. As covered above, large quantities of water-based gel will break the fat emulsion. Switch to oil-based colouring for deep shades.
2. Temperature. SMBC is highly temperature-sensitive. If your buttercream is too warm (above roughly 24°C) when you add colouring and mix, the fat may separate. If it is too cold (butter still firm), the colour will not incorporate evenly. Aim to colour your buttercream at room temperature — firm enough to hold peaks but soft enough to mix smoothly.
3. Adding colour too fast. Add colouring a few drops at a time with the mixer running on low, rather than dumping in a large quantity at once. This gives the emulsion time to accommodate the addition.
If your buttercream does split while colouring:
- Stop adding colour immediately.
- Increase mixer speed and beat for 2–3 minutes — the emulsion often re-forms with mechanical mixing.
- If it is still broken, the temperature is likely the cause. Refrigerate the bowl for 10 minutes to firm up the butter, then beat again.
- As a last resort, gently warm the outside of the bowl with your hands or a hair dryer on low for 20–30 seconds, then beat on high.
See our guide on how to colour buttercream with gel, powder, and liquid food colouring for a full breakdown of when to use each colourant type.
Dark Colour Combinations That Work Well in SMBC
Some shades are hard to achieve from a single colour alone. Here are combinations that work reliably with Colour Mill Oil Blend:
- True black: Mix Black with a small amount of Dark Brown or Navy to build depth and reduce the grey cast that pure black can sometimes give.
- Deep navy: Navy base plus 2–3 drops of Black. The black removes the brightness and gives you a true dark navy rather than a royal blue.
- Forest green: Leaf Green or Sage base plus a small amount of Black. Adding black to any green shifts it from bright/lime toward a rich, deep forest tone.
- Deep burgundy/maroon: Burgundy or Red base plus a small amount of Black or Violet.
- Chocolate brown: A good mid-brown base (Chocolate or Mocha) plus a few drops of Black for a richer, darker finish.
In all cases: mix, check the colour, then rest overnight before deciding whether you need more.
Starting from a White Base Makes Everything Easier
One underrated tip: if you are going for a very dark shade, starting from a whiter buttercream base will give you a more accurate result and require less colourant overall.
Standard SMBC made with unsalted butter sits at a natural pale yellow/ivory. That yellow undertone fights dark shades — it can make deep navy look greenish, and true red look orange-red. If dark colour accuracy matters to you, consider adding a small amount of Colour Mill White to neutralise the butter tone before adding your target colour.
Read our guide on how to make white buttercream for specific techniques and product options.
The Bottom Line
Getting deep, dark colours in swiss meringue buttercream is entirely achievable — but it requires the right colourant and patience. Use oil-based colouring, add incrementally, stop earlier than you think, and let time do the rest.
Shop the full Colour Mill Oil Blend range at Baking Pleasures — available in individual 20ml bottles and sets, with fast Australia-wide delivery.
Shop Colour Mill Oil Blend