How to Color Buttercream

1. Make the buttercream first, uncolored, and bring it to the final consistency you want before adding any color, since color is much easier to judge against a finished texture than a half-mixed one.
2. Dip a toothpick or the tip of an offset spatula into gel paste such as a gel paste color kit, and add a small amount to the buttercream. A little goes further than it looks like it will.
3. Mix on low speed until the color is fully even, with no streaks or darker patches, scraping the bowl once partway through.
4. Stop and wait 10 to 15 minutes before deciding whether the shade needs more. Gel paste continues to bloom into the fat during that time, so a shade that looks light straight off the mixer is often close to right once it settles.
5. Add more color in small increments if needed, repeating the mix-and-wait step each time, rather than adding a large amount at once to chase a target shade quickly.
6. For deep or dark colors such as red, black or navy, expect to add considerably more gel paste than a pastel shade needs, and consider mixing the batch and letting it sit, ideally overnight, before final judgment, since these shades keep deepening the longest.

Liquid supermarket food coloring is mostly water with a small amount of dye dissolved into it. Buttercream is an emulsion of fat, sugar and a small, carefully balanced amount of liquid, so adding extra water from liquid coloring throws that balance off, especially once several drops are needed to reach a strong shade. The buttercream can turn noticeably softer, occasionally even split, from the added liquid alone, on top of usually needing far more drops than gel paste to reach the same intensity of color. Gel paste sidesteps the problem because it carries almost no water relative to its pigment load, so a strong color needs only a small amount added.

Red is the color most likely to shift after mixing, and the usual cause is a gel paste that is not formulated to resist fading, combined with time and exposure to light and air. A cheap or older red can oxidize slightly as it sits, drifting toward a muddier, more orange-brown tone, particularly under warm event lighting that already skews colors toward the red-orange end of the spectrum. A fade resistant gel coloring formulated specifically to hold a true, stable red under those conditions is the more reliable choice for anything that has to look right hours after mixing, such as a wedding cake finished a day ahead.

Mixing the red buttercream well ahead of when it is needed, rather than at the last minute, also helps, since it lets you see the color it will actually be by the time it is served rather than the color it was straight off the mixer.

True black is one of the hardest colors to reach in buttercream because it needs an unusually large amount of gel paste to get past a muddy dark brown or grey stage, and it is easy to end up with a bitter, slightly off taste from that much concentrated dye. Building black up in layers over a day or two, letting each addition deepen before adding more, gets closer to a true black than trying to force it in one sitting, and starting from a chocolate buttercream base rather than a plain white one needs noticeably less added color to get there.

True white runs into the opposite problem: American buttercream naturally takes on a pale ivory or yellow tint from the butter itself, so a small amount of white gel coloring is usually needed just to neutralize that tint rather than to add color in the ordinary sense. A high-ratio shortening based buttercream starts whiter to begin with and needs less correction.