Yep! I used the same type of method "rasterline interrupt color changes" on my C64 in 1983.
And it was very VERY useful on the Atari 800/400 computers which had a palette of 256 colors! And no HAM mode. So every good coder did "dynamic hires" on Atari 8-bit computers. These are the computers that competed against the C64 and Apple ][+
The Atari 400 and Atari 800 chipsets were designed by Jay Miner who then took the idea to the next level in the Amiga.
Although strong vertical design was stressed, changing color registers at the end of each scan line during horizontal blank was not always the best method.
Page flipping 2 screens offered more colors without the overhead. Just 4 load and stores for color and 1 load and store for the page flip. That left plenty of VBI time for other routines.
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