Question

What will happen to the Rf values of the pigments if you were to increase the relative concentration of acetone in the developing solvent

Answer 1

You haven't told us enough about what you are doing to be able to answer the question.

Answer 2

Increasing concentration of acetone increases the polarity of the solvent. The distance travelled by the pigment on the silica or alumina will be larger.
Rf = distance the pigment travelled/distance the solvent travelled
So Rf value increases.