At my last job we painted antennas for some projects. I don't believe there was any issue with performance.
As far as painting radios, though, you want to be careful that you're not adding a color which absorbs more heat as it could cause the radio to overheat and damage electronics. In other words, don't paint a white radio black if it's going to be baking in the sun.
The alternative is to put the radio in another enclosure, like a non-metallic NEMA box, and run the antennas out from it, since all those exposed devices can be painted. We typically used indoor radios in a weatherproof box for this.
And if you're going to paint these things, be careful what sort of paint you use. Regular spray paint will flake off of plastic components, so you'll need to use specialized paint. We have a guide on painting gear you should refer to before making any decisions.