1:The design(s) could easily be turned into recolourable channels, rather than a non-recolourable part. See this tutorial for instructions: Basic Mask Editing.

2:It's not clear from the post text and pictures whether or not the design(s) are recolourable in CAST. There should be at least one picture showing the item's ability to be coloured, and some text describing the number and description of recolourable channels (even if that's "None, it is not CASTable.").
2:While some parts of the design are CAStable, there are other parts which aren't CAStable and could easily be made so, or which don't make sense as a non-CAStable area. See this tutorial for instructions on adding CAStable channels to your item: Basic Mask Editing.

3:While some parts of the design(s) could probably be done as channels for more versatility, it's not strictly necessary and it's understandable for the design. There's a tutorial on recolourability here: Basic Mask Editing, in case you'd like to try it in future.

4:The design(s) have non-recolourable parts, but it's understandable for the item and would be difficult or impossible to make work as channels.
4:The design(s) are fully recolourable, although they would be more versatile if you split some parts off into separate channels. Nevertheless, the CAStability is good and flexible.

5:The design(s) are all fully recolourable and nicely versatile.