I bought some second hand G25's a few years ago. They were black dot, can't remember which dot was supposed to suit me best but it wasn't black. I looked into getting them altered, Ping offer to do it I believe, for a charge, but then @bobmac asked how I was hitting them. 'Quite nicely' was the reply. 'Don't do anything' was the response. Wise words
Red and black dot are next to each other on the Ping chart. As Bob says above, the difference will be too small to notice.
If they don't suit then either sell them or take them to a pro and ask to see how they work for you. If they need altering then I suspect any alteration will be more than one colour.
