Really well done, but I agree with one of the comments in there: need to add patterns to the solid colors; it would differentiate for color blind folks and in general make the relationships easier to grasp.
I tried pasting the cross join and inner join into a colorblindness simulator [1] and the only issue I found is that the A and the 2 in the cross join look similar if you have monochromacy. Looking at the monochromatic version, I don't think this really affects the clarity of the cross join diagram.
The inner join is already perfectly distinguishable by how dark the squares are, and anything other than monochromacy preserves the distinctions that the color adds in the cross join, unless the site I used is misleading.
The inner join is already perfectly distinguishable by how dark the squares are, and anything other than monochromacy preserves the distinctions that the color adds in the cross join, unless the site I used is misleading.
[1] https://www.color-blindness.com/coblis-color-blindness-simul...