The digit summing is generally similar to Fibonacci summing (though I do it on the individual digits usually, not the full numbers, e.g. 8+13 = 12 instead of 21).
Any particular reason why the colors flipped for the 34x55 rectangle? Is this a different part of the pattern? I can see in the larger header that there are regions with single white squares (as seen in the 34x55 rectangle), just as there are regions with single purple square (as seen in the 8x13, 13x21, 21x34, and 55x89 examples).
This will be a long read that will take me a few days, so I'll leave this comment now.