If he's a male, and their females, then very normal behaviour.
The fact that their sunsets and he's a red wag won't worry him or
alter his behaviour at all.
You'll just end up with a cross of the two colours when the females breed.
If the sunsets are also male, then he is the dominant male platy in the tank and
is exerting his dominance over them.
The best ratio IMO is one male to 3 females which helps spread the hassle factor for the females