I have never noticed a change in color when first applied. A long time ago both products would yellow with age, but they seem to have fixed that problem quite some time ago, and have had no yellowing with either for a long time.
I haven't noticed any yellowing but to me it seems to darken the paint quite a bit. I used Russsian armor green on a Japanese Jack and before glosscoat I thought it matched the box cover art very well. After it looks a lot darker to me