Try going to Image then Adjustments and playing around with the settings there. Like Hue/Saturation or Color Balance. I haven't edited any screencaps myself but that's what I do when I want to adjust my painting's colors and play around with different effects.
dunno if this is helpful for you but when you upload pictures to some kind of host, for example imgur, you can choose some effects in editing and it'll be automatic.
There's an easier way, just email it to yourself or something and use your phone on the app "magic hour" it has a bunch of cute pastel fonts and animal crossing fonts and you can make your own font c: