I was wondering why when you color buttercream a darker color it taste bad and very bitter. Is there anyway to stop that from happening?
The bitter taste is coming from the large amounts of color you have to use to get the darker shades. I have never tried powdered colors or colors for candy, but I think those may be less prone to give you that bitter taste. Maybe someone more experienced than you and I will respond. I do know that if you color your buttercream and then let it sit for a day, it will darken a fair bit. Sorry I'm not more help.
Along w/the other advice, start your dark/bold colors with a lighter base.
As an example you want brilliant red, don't just add red paste/gel color to white icing but 1st tint it a very good pink, yellow or orange, then add red to that. It helps cut way down on how much red one needs.
The same w/navy blue, brown or black. Start by mixing together any and all colors of icing you have on hand - yes, it will be an ugly color but now you add your blue, brown or blk - again it won't take nearly as much color to achieve what you want.
For those I save all my little dibs and dabs of icing when I'm finished for the day - any amount *less* than 1/4 cup; I save it in a glass container in the fzr - adding to that each time I finish a decorating project. When I have a need for one of those dark colors I pull it out, give it a good stir and add whatever color I'm going for - black, blue, or brown. You also can add some UNsweetened cocoa powder - especially if wanting drk brown or blk; mix it 1st to a thick mud w/some *hot* water, then add to the icing.
I know that the wilton colors will do that to get a dark color. I started using americolor gels and will never go back to wilton. You need to try different brand as it seems that each person has their own preference to what kind of color they use.
And half the time the color does not look anything like the color on the label sigh. Its embarrassing to make bitter tasting icing. Wish people would want light colors lol.