Bowgun ammo color?

Ok, this is driving me insane! Why does some ammo have a red background when selecting and why do most have a blue background? When fighting the great baggi the flaming s ammo is red in the UI. When fighting some other monster 2 or 3 ammo types may be red and the rest is blue. I can't find any info on this anywhere. Help!

(This is my first MH game. Heavy Bowgun user.)

The ammo being a different color means that you can siege mode fire it (is it called crouching fire now?)

CarmineRed wrote:

The ammo being a different color means that you can siege mode fire it (is it called crouching fire now?)

Thank you!