OK, somebody had to go and mention Mondrian (THANK you for the compliment!) when I posted Not All Rectangles Are Square
a little while ago, and so I could not rest until I had this to add.
I did say I had thought of Mondrian while I was working on the white and black abstract, but it did not immediately come to me how and where the color was to be added. But it nagged at me and, at 2 a.m., way past my bedtime, I opened the first picture and it hit me, just like that. So. Here is my Mondrian tribute, and my thanks to van049 for the nudge.