I know there is a 95% you will not like this answer but we have... deco.
There are already grey powders, like STNE and CNCT. (This is a common problem with adding new elements. It's hard to find a color that is realistic and stands out from other elements. There are too many tan, brown, and grey colored things in real life)
You can press H to see what element your mouse is pointing at.
DUST is based on POWDER from other powder games. It is always the same color. Just image that it's sawdust or something.