Answer:
1)Gray. The color emphasizes the bleakness of the media room and Mildred's most precious world.
2)Green (or soft green light). The color emphasizes the healthy vibrancy of the natural world.
Grey color gives the reader a sense of bleakness, solitude, of nothingness. The green color, on the other hand, represents life. All that is natural, the green color of leafs, of trees, etc. The contrast in this two situations affects Montag because he feels bleakness in the media room but he feels the life in the park, in the outside world.
It could be represented as his personal conflict throughout the book.