We all have to work towards making inclusion an ordinary occurrence. Rather than wonder about how to adequately represent exactly 17% colored people in an image that only has three people in it, chill out and drop some extra color in there. You are neither atoning for hundreds of years of continued injustice, nor creating institutionalized racism against white people. You’re just making the world a little friendlier for the many, many people alienated by their media. Don’t overthink it, just go for it.