Some sources I found say at in an indo-european culture black and white where the same word of "blace" but the c and e where a compound letter.
I'm not quite sure what letter you're referring to, but it's the case that we have one Indo-European root that gives us modern words meaning "white" and "black": *bĘ°el-. The root originally meant "burn, shine", and we see one of these meanings attested in e.g. Latin flagrare 'to burn'. The meanings of this root developed in two opposite directions in various forms in various languages, so you went from "burn" to "having a burnt color" to "black" on one hand, and "shining" to "bright" to "white" on the other. English has a native doublet, black and bleach, exemplifying the two paths.