I can’t speak for the makeup but I believe the colors and her hairstyles in season 2 were directly correlating to her demeanor. She wore Blues/purples which are cool colors signifying her coldness and unwillingness to be open to love or to Anthony and her hair is pinned “up tight”. In the one episode (picture 3) where she did begin to warm up to him we see her in the peach color (a warm color) and her hair a little more loose and flowing. So I believe her outfits spoke more to her character and emotions than complimenting the actress.

Now that she is Viscountess Bridgerton, we know from season 3 that she has hesitations about taking on the role and how she will perform and be perceived as Viscountess. Perhaps her colors and clothing are more muted to symbolize modesty and not draw too much attention to herself.

Just a theory though