All games have gimicks. Kanon had its snow. To Heart has it's trademark red uniforms. There are games that follow the Maid gimick or the Nurse gimick or the (rather disturbing) loli gimick... its hardly anything unusual. And each game has some sort of structure to it, like the whole 'which one will he want to marry, god or devil' in Shuffle or 'which girl was it that wrote me that note' in Sentimental Graffitti... gimicks abound. its part of the genre.
I think the idea of using color blindness as a kind of metaphor within the game is at least somewhat original, not sure if any other ren'ai game has used it (or the potential it has for an interesting color pallette for the design of the game :) Gimicky indeed.