Originally posted by Sephiroth
i agree with tom there.
look at iron oxide.. its red.. and could be used to make orange paint.
the most common metal oxide colours are , red, white, and black.
but then there is copper..
Based on the colors I have seen in paintballs I am 100% sure that they mostly use (food grade) organic pigments as colourants. Only white and black are the colours you can't get with organic pigments (for those colours you use titanium dioxide and carbon black mostly).
The difference in colours between inorganic (metal oxide) pigments and organic is pretty large. Most of the paintballs have very bright and "clean" colours, whereas the inorganics are commonly not that bright in colour - yellow iron oxide for example is more ochre-like in colour.
JoseDominguez: The chalk is used to enhance the whitening power of titanium dioxide - at least in "normal" paints, not the other way around (a bit long to explain).
Chalk makes the paint thicker, cheaper and "better covering". It is a better idea to put some chalk to enhance the colouring power of titanium dioxide (or any other pigments as well) than to add more of the pigment.
I think you can make the fill of a paintball to separate if you let it stand long enough - at least I recall to have seen paintballs where there has been some separation. I would not be too concerned about that anyhow - simple solution should be to turn around the paintcase every now and then if you have to store it for a while. I do not think that they would add chalk - or any other filler - in such amounts that they would sediment. The fill is also usually so thick that it does not normally separate.