I’m making myself a small bday cake for my 40th this week. It will be choc/w choc buttercream. I want the frosting to be black and red. I have Wilton red gel food coloring in a dropper bottle and black gel in a tub. These both have strong flavors. I plan to use some Dutch processed coco that’s a dark brown, but to get the saturation I’d like, I’m afraid the icing will not taste as good. Are there options to mask the flavor? The stores have been out of no taste red every time I have been shopping...

Black is a combination of ALL colors  One of the best ways to make so there is little to no taste is to save all your tiny dibs & dabs of ANY & ALL color icing when you are finished with any project — even as little as a teaspoon—in a jar in the freezer    A couple of days  before  you need black take it out & stir it well   It will be n ugly color but never fear just add some black  coloring - you will need much less than you think & WAY less than starting from white    It takes time for the color to “develop “ so it needs to sit a day or two to see if you need to add any more    If making it “from scratch “  1st color it a good deep blue or any other dark -even green before adding the black

To make red again start at least a day or two before   Add pink yellow or orange 1st before the red   Again this is so you don’t have to use so much red   A trick I’ve used is to add UNsweetened Kool aid powder — black cherry or strawberry is good - if you don’t mind the flavoring   An even older trick is adding cinnamon :)   

At the expense of raining on your parade, you can't make chocolate frosting bright red.  At best, it would be muddy.  For the red, I would start with white and go from there.  Since you are using a dark cocoa to start with, it should not require enough of the black color to make the taste noticeable.  

Of course Sandra!  I just didn’t think about the mention of wanting the red to come from the chocolate icing —can’t be done:(    The red would need to start from plain icing then tint it pink orange or yellow before adding any red    I also thought of another option if a small amount is needed  — buy a one of those Wilton tubes for writing then cut off the back end scrape it out and mix it with 2x or even 3x as much of any of the colors mentioned already   That icing is sooooo saturated with color    One other thing to mention — any icing that has that much color is going to stain the teeth lips & any clothing:(  

to me the best option is to use black cocoa -- it's the kind they make oreos out of -- can be found on amazon -- not sure where it's available elsewhere -- you will still use a lot of food color to make regular cocoa icing black -- you use less or none using the black cocoa -- and yes you need to start with white icing to make red -- there used to be a "no taste red" color -- airbrushing or painting is even better --

Just reread your post again  & noticed that the colors  you plan to use are gel   Unless I’m misunderstanding  &/or they are a new Wilton product  I haven’t seen they will not impart the deep color you are looking for   Those  Gel  tubes are clear (see through jelly-like ) & NOT very dark - it won’t help much to color  when added to icing & won’t show if used to write on any color except white    The tubes I referenced in the above post are filled with icing not gel  

I did forget to mention that airbrushing is a wonderful alternative and will not impact your teeth and tongue so much.  If you don't have an airbrush, Wilton makes spray colors that work very well.

Bump 

I've made red buttercream with chocolate and had no issue, but I wanted more of a burgundy. I only did it that way because the buttercream needed to be chocolate, but it worked. For red, I usually start with pink because it is easier to go from pink to red than white to red (for me), I always ended up using waaaaaaaay too much to get there. I do try to make darker colors earlier in the week so that it has time to deepen and I can add more if needed. For red, I use Americolor as my preferred brand. 

Since I am a hobby baker, I use Wilton gel colors because they are locally available, except for black.  I use Americolor for black because Wilton black looks like a cankered green after an hour or two.  I probably should invest in a bottle of red, too.

Americolor is the only black that I have found that doesn't have that weird green to it. My Wilton black was clumpy and odd after a week!