I think there was some sort of color support prior to System 7.

kagis

https://en.wikipedia.org/wiki/Macintosh_II

System 6 includes QuickerGraf (originally QuickerDraw), system software used to accelerate the drawing of color images on the Macintosh II.

Hmm. Apparently System 4 had color support, which is earlier than I expected.

https://www.reddit.com/r/VintageApple/comments/1bsttma/why_did_apple_wait_so_long_to_implement_color/

...it wasn't until two years later in 1987 that Apple introduced color with the release of the System 4 & the Macintosh II.

Here's a photo of a IIcx with a color display:

I share the same feeling. The flat lifeless interfaces need to go.