I think Roll kinda stands out too much. She is the only one with a black outline, and she uses 5 colors, while Dr. Light and Dr. Wily only use 4 and Megaman uses 3. Sure, it's possible to do on NES, but that's a rather large sprite just for a dress. The extra shade of red doesn't seem to have enough contrast, as well. Maybe something like one of these would fit better:
Both have been reduced to 3 colors, and show with and without the dress highlights.
Also, looking at that jumping frame of Megaman in the attachment, I think the darker blue looks better, but doesn't look too dark that it wouldn't work against a black background, which are very common in NES games, though Castlevania has a lot of dark blue skies, too, so it might help to just change the lighter blue to a cyan.
Both have been reduced to 3 colors, and show with and without the dress highlights.
Also, looking at that jumping frame of Megaman in the attachment, I think the darker blue looks better, but doesn't look too dark that it wouldn't work against a black background, which are very common in NES games, though Castlevania has a lot of dark blue skies, too, so it might help to just change the lighter blue to a cyan.