Crimson Fists are darker blue than Ultramarines, a bit more royal as you say. According to
GW tutorials, Crimson Fists start with Kantor Blue. Of course, if you want you Crimson Fists to be little lighter in color, nothing's stopping you!
As for blue chapters other than Ultramarines, maybe this will give some inspiration:
https://www.deviantart.com/djnnayt/art/All-Loyalists-Space-Marine-Chapters-425805126 There seem to be a lot of chapters that have the exact same color scheme as Ultramarines, with just different icon. But if that's a little boring, how about Novamarines or Eagle Warriors (though they are half-white, which can be tricky to paint..)? Or the really old school Rainbow Warriors?