Please can you help me to answer this question about colours and graphics?

They are representing the amount of each of the three primary colors (RGB) with a real number from 0 to 1. White is 1, 1, 1, i.e. all three colors at full intensity. Red is 1, 0, 0, i.e. red at full intensity an no green or blue. The average of those two values (pink) is 1, 0.5, 0.5, which you arrive at by adding 1, 1, 1 and 1, 0, 0 and dividing by 2. To divide 2, 1, 1 by 2, divide each of the three color components by 2.