Have your ever heard of ctype? Yeah. You don't need deco color.
Using FILT's heat-to-color feature is really niche. The only reason I'd use it is to visualize heat without heat display.
Purple PHOT can be achieved by setting the ctype of PHOT to 0x20000001. Orange PHOT can be achieved with 0x20040000.
I'm really sad that this wasn't brought up earlier. Maybe it's a fact more localized to the subframe community.