Hello Nat,
What do you mean by one of each size?
Of all the colors offered of the current battery power monorail, I have only the red, and that's enough for me. Although the motor system is OK, it would have been much better with transformer power.
The uncommon, unpowered toy set that was sold in the early 90's... I have only the lime green and the tape stripe is starting to shrink. It was offered in a lot of different colors too.
I have both a red and blue Schuco set, and a silver train only. I like the MK 1 the best.
But if Disney ever offered a very highly detailed, static model of the MK 1, in O gauge, in both red and blue... yeah, I would have to have both of them!