Color Managed Color Parameter

## Standard Change Workflow
- [x ] Create proposal as issue (you're doing this now!)
- [x ] Tag this issue with `standard change` tag

## Summary

After we release colorspace suite, we should follow up with color managed color parameter.

## Example use cases:

set a red rectangle - user might think in terms of 1,0,0 but the actual given working process colorspace might not be intuitive.
pick somewhere on screen to get color somehow
set a threshold value slider
make your own custom widget (e.g. HLS)
map OS supplied color picker (some do that I think when you click on color param)

## Problem

likely requires a host call back to return to us chromacites?...
perhaps color are always define in linear internally?
host might support different display options if they popup a color param editor for such param

Start by reviewing the colorspace suite referenced in the issue and the unresolved discussion about host callbacks, chromaticities, linear internal colors, and display options. Done would require an agreed color-managed color-parameter design covering the listed use cases, rather than an implementation based on the current proposal alone.

Written by the indexing model from the issue text.