[Fluxus] rgb & hex colour conversion

[gabor papp]

thanks for the conversion functions. they are working fine.

> depending on whether #aarrggbb should be  converted to #(a r g b) or #(r
> g b a) the above might need to change a bit.
at the moment fluxus uses #(r g b a), which might be a bit strange if we
expect the hex string in argb format as "#aarrggbb". although i think
this is pretty standard. processing also expects colours this way.

> i would suggest going with the more widespread 'html' convention as
> default, rather than the PLT compatible representation.
sure.

best,
gabor