It is can be very daunting, it might even stop someone from buying a straight razor. The different colours, different strops, how to hold a blade, how easily you can wreck a strop by holding it an a wrong angle. But like riding a bicycle, once you get it- it comes like second nature. This post we cover strop paste - this is a general summary of what the different colours mean and how you should use them.
Yellow - leather balm (just for maintenance - non abrasive, keeps strops smooth and supple)
Black - Fine grit
Red - Medium grit
Green - Most abrasive
White - For canvas side (non abrasive, fills in fibres provides smooth and even surface for warming up the blade before stropping on leather side.)
I wouldn't mix green grit with anything else, i'd have a strop especially for that one.
So in a nutshell - if i had a slightly dull blade that doesn't need professional honing on a stone; I’d do, white - green - red - black.
Do watch plenty on videos before stropping for the first time and go slow.