I just got an old Rainbow swing set from a neighbor. The swing set is stained as red and some stain is off. I want to restain it with blue. My original plan is to remove all the old red stain but it turns out to be quite time consuming. I did some research and it seems it will fine to paint over old stain as long as the color is darker. The problem is that I don't know if blue is darker than red.

Any suggestions? I don't mind to restain it with the same red but just prefer blue.

Thanks.