Thats a very good idea, I was looking at ideas around the number 3 also. I found it funny to explore possibilities around a theme.
And yours are good ones.
As for colors, my preferred is the last one (gray tones), a cube with a little "cartoon-ish" side.. looks great!
Thanks @eternalsunshine !! I jumped through a lot of thinking hoops to get there ! it's all about the magic of the number 3 which on reflection is also a triangle shape :)