The little bottles on the right hand side are the cartridges the gun dispenses from. Red tipped cartridge holds ketchup and the yellow one mustard. The gun in the pic is currently loaded with a yellow tipped cartridge (seen sticking out of the muzzle) and is therefore correctly dispensing mustard.
The gun just happens to be colored red. You want a yellow gun, go make one yourself.
Marketing Consultant: No, King Condiment, you can’t put red in red on an ad. They won’t see it. They’ll wonder why you’re selling a gun to shoot at food.
The King: But it’s great advertising!
Marketing Consultant: No, that’s not a great marketing ad.
The King: But they can still use red for ketchup right?
Marketing Consultant: Of course. And your instructions can tell them which is for which.
The King: It’s so confusing!
Marketing Consultant: It is. And if you had hired us before manufacturing millions of these we could have told you about using another base color with red and yellow grips and triggers. But you didn’t and so here we are.