"To paint a room" means to apply a layer of colored paint to the walls, ceiling, and maybe even the floor of a room to make it look different and more attractive. Full definition
I love this color so much I'm actually thinking of painting another room in our home with it! (findingsilverpennies.com)
I especially love the white painted room with that single black chair (good to hear your favourite white — I'm always on the hunt for the perfect white). (vanessafrancis.com)
Although I usually go for color, I decided to paint this room white so the doors would really stand out. (atthepicketfence.com)