The red chocolate menace is slowly killing me.
The first thing for me to consider was the source of red color, if not using artifical dyes. Most berries, from cherries to cranberries, have anthocyanins for color and beets have betacyanin; both are red in acidic solutions, but purple in basic solutions. Purple added to chocolate does not work, so I kept a slightly acidic environment. Unfortunately, I forgot that heating table sugar in acid causes some of the sucrose to be cleaved into glucose and fructose, which keeps the solution from crystallizing and left me with more of a jam than chocolate.
What I needed was something true red and soluble in fat, rather than water. Three or four possibilities came to mind: lycopene from tomatoes or watermelon (or guava or pink grapefruit), astaxanthin from krill oil (and maybe red kelp) and iron (II) oleate, which is probably best not thought about. The krill oil was a non-starter; expensive, liquid at room temperature, slightly odd taste.
So... I went on to try to pull the red color out of tomatoes without bringing along too much of the flavor compounds or acids. My Evil Kitchen doesn't have steam distillation or centrifuging capabilities (yet), so I resorted to some very old techniques. I now have pasta sauce that smells oddly of chocolate. I have quarts of it. Quarts and quarts of slightly odd marinara.
Now it's personal [cue ominous music]. I will have red chocolate by Easter, if I have to use my own blood. Hmmmmm. Hadn't thought about heme for color. [cue very ominous music]