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.
Ummm which 1337 distro we talking about, friend? There’s only one line.