What I thought was decent:
*Interesting and unusual incorporation of theme.
*Nice font, button graphics, and sound effects in the UI menues.
What I did not like:
*Gameplay lacks entertainment. For the easy and hard modes, I did not like that there is no end goal in the gameplay. For the timed version, the time limit is way too short. I would recommend making the easy and hard mode timed versions, and then eliminating the original timed version altogether. I also would recommend adding personal high score in the game. Also, blue should be called dark blue at least in the hard and timed version. That is because I think it is unfair for someone to confuse light blue with the blue the game is asking for.
*Graphics are too simple. I would recommend having a fancy background. The colors can be gradients, in where the top color is a lighter color while the bottom color is a darker color. The fancy font in the UI menues can be used for the font of the score (and time left on the timed version).
*Not much sound in the game. This game would have been much more moody with some music. Also, the soundeffects are only used in the UI menues. It would have been much better if there were sound effects in the gameplay (perhaps when clicking on buttons).
*UI menues do not look too professional. The UI menues should have titles and backgrounds.