It's about 60% blind luck. However, you can see that Colorado is a bit wider (or taller, since they're rotated ninety degrees), especially since they're right next to each other for comparison.
This is not my map- I simply made a quiz using a map by XKCD- see the link in the quiz description. As such, I won't add HI/AK to it- though maybe you could swap Hawaii and the Aleutian islands?