It’s obviously a variation of Ultramarines insignia. Hitch will purge in the name of the Emperor!

You’re going about this as a human, you need to think about the show universe to understand cutie marks.
 
 
The “green pony backsides” are clearly hearts, showing he has a caring side.  
The “rocket ships” are/is a shield, showing he’s a protector at heart.  
And the “omega” is obviously a hoofprint, it’s the classic horseshoe shape, combined with the other symbols, it means his personality is a strong caring protector. he can take hits, and will fight to the bitter end for what he cares for.
 
 
(Disclaimer: I have not watched g5 yet, I may come back and edit this if I ever do watch g5 and am wrong)

But the background is the color of the sea… sea… C… C for Catwoman!

What kind of idiot would think thats what hitch will be like

its a shield pal

Always remember to stretch before jumping to conclusions.