hi there, i am new to diving and just bought my first reg..mk25 first stage,plus S550 second and S550 octo.....only thing, cant really tell the difference between the second and the octo.SP catalogue says all octos are bright yellow, mine aint....i think the octo is a light grey, all plastic and the second is a dark grey with a stainless "S" in the middle....would appreciate if a dealer or someone with more knowledge could clear it up for me....thanks.