[Suggestion] RGBA equivalents of XYZW material nodes

Flax has several material nodes that use the component names `X` `Y` `Z` `W`, examples are the `Mask` nodes as well as `Pack Float4` and `Unpack Float4`. When working with colors, this leads to the situation where you're using two different names for the same components. It would be best, in my opinion, to use these different names in different contexts.

My suggestion is the addition of `Pack Color` and `Unpack Color`, these are functionally equivalent to the existing `Float4` versions, but would use `R` `G` `B` `A` component names. As well as `Mask R`, `Mask G`, `Mask B`, etc. which would be equivalents to the existing Mask nodes.

Locate the existing Mask, Pack Float4, and Unpack Float4 material-node implementations and inspect how their component names are defined. Add the requested color-named equivalents with R, G, B, and A components, then verify that they behave like the corresponding Float4 and Mask nodes.

Written by the indexing model from the issue text.