Echo devices did indirectly give you some color control before, letting you select pre-programmed "scenes," which would change the color, dimming and other factors on the Hue. How, however, now all you have to say is "Alexa, set the bedroom light to orange," or "Alexa, make the living room warmer," and it'll execute those specific functions.
Similar commands work across the Hue, TP-Link Kasa and LIFX bulbs, it appears. Alexa will remember up to 100 shades, including things like "warm white," and other practical colors more useful than "red" or "purple" (depending on what you're up to).
The "skill" puts Alexa on par with Google Home, which has been able to change smart bulb colors from day one. The update is now live, and also works with other color changing bulbs you might be using via the SmartThings platform, too Amazon notes.