Please add the ability to change the color of a lightbulb with emulated hue bridge with Alexa. Color changing is now supported with Alexa for Hue, TP-Link, and Lifx bulbs. When I ask Alexa to change the color of my emulated hue bulb she says it isn’t supported.
Here is a link for more information: https://www.cnet.com/news/finally-alexa-can-change-the-color-of-your-smart-lights/
More relevant info available at https://developer.amazon.com/public/solutions/alexa/alexa-skills-kit/docs/smart-home-skill-api-reference#setcolortemperaturerequest and https://developer.amazon.com/public/solutions/alexa/alexa-skills-kit/docs/smart-home-skill-api-reference#setcolorrequest
This isn’t going to be supported on Alexa ever. Alexa only supports colors with skills. The built in non-skill way that Alexa works with Home Assistant does not support colors as it is only for older bridges. Everyone with the v2 (square bridge) has been told to get the official Hue skill because of new features.
Sorry to disappoint 
So would it be possible to do this with a custom built Alexa skill? Or is it really only something that would work with an “Official” skill?
It can work with a custom built skill like Haaska. I added color support recently to it although it hasn’t been merged yet.
Commit was merged: https://github.com/auchter/haaska/pull/37#event-1063159803
To clarify: Does the “old” bridge that HASS emulates support setting colors? Could Amazon update their non-skill way to support setting colors?
Nope, and Amazon has said that method will not be updated again, so I wouldn’t expect that to change.