I constantly do this stuff, even with Kool-Aid. Mix grape and black cherry together. See if you like it.
(Sugar) Cookies were my main laboratory. I made rootbeer float cookies, blueberry muffin, orange and creme, and a bunch of other variations. The method is to make two half-batches of sugar cookie dough, coloring and flavoring each separately. For the muffin part of the blueberry muffin cookies, I used butter flavor shortening, and a bit of butter flavoring. Actual butter would have made the cookies into jerky. Anyway, when you have your batches made, you can either take a pinch from each bowl and put the pair on your parchment if you're feeling lazy, or go even further beyond. Roll out and square the corners of your doughs, then lay one atop the other, and roll them up. Then you roll out the dough so it becomes a long cylinder, maybe a couple inches thick. Cut this cylinder to a convenient width, wrap in wax paper, and freeze overnight. The next day, you just slice cookies off of the roll (after removing the wax paper), and optionally press one side into sugar crystals, then bake for 7-9 minutes on parchment paper at whatever your recipe's temperature is.
I recommend watching cooking videos for ideas, and not necessarily the sterile, professional kitchen kind. I recommend Cowboy Kent Rollins and Townsends. I started making all kinds of stuff after seeing dozens of their videos and recipes.