Heather mixes two white liquids together. Immediately, a gray liquid forms. How is the gray liquid related to the white liquids?

The grey liquid is related to the white liquids because the change in colour is the result of a chemical change/reaction between the two white liquids.

The problem here is that according to aufbau principle before 3d orbital 4s subshell comes.after filling 3p orbital with electrons you have 4 electrons left, you place two in 4s with opposite spin and the other two in 3d in any of its two orbitals of total five orbitals with the same spin.