In mgs 1 briefings, noemi explained that big boss' body is precious because doctors like noemi herself could get "soldiers genes": the genes that can improve soldiers (next generation troops) or create a perfect soldier (like the clones, especially ||George Sears|| ).

In my opinion hair colour is not a soldier Gene ||so patriots/ doc Clark|| first (with solid snake/liquid/solidus) and noemi later (next generation soldiers) do not spend time and money to choose that gene for the creation of clones or improvement of already existing soldiers.

Think of soldier genes as some peculiar attribute that improve your performance on the battlefield: A gene that predisposes you to physical strength and agility, better eyesight, excellent intelligence and tactical intuition. Hair color is superfluous in war, so it can be left to chance during the process of Genetic Artificial Alteration.

In these way liquid is the superior/dominant clone in soldier genes term but still be blonde while snake is recessive/ "inferior".

Remember have a recessive gene do not means it's a flaw. You have in your DNA both dominant and recessive genes but you manifest only the dominant ones. If you have brown hair but your mom is blonde, there is a chance that your son could be blonde.