Originally Posted by matrix-cat
He has long hair in the mission briefing, which isn't in colour, and at the end he asks Naomi for a pair of scissors so he can cut his hair. He never asks if she happens to have any brunette hair dye on her.
Originally Posted by Gouda Jouji
He only cuts it in MGS1. He never asks for hair dye. The coloring of his hair in the MGS1 briefing scene is probably a mistake, or just lighting. Plus, in Metal Gear 1 & 2 his hair is brown.
That's early Pliskin concept art. Snake was originally going to dye his blonde to further disguise himself in MGS2.
You don't need to see him dye his hair right there and then. He isn't in a boutique. He is also the clone with the recessive genes. Blonde is recessive.
As Pliskin, he was suppose to have his blond hair also. What's more likely is...
Originally Posted by StuBurns
Those kinds of things can't really be taken as fact anymore though. The games are retconning huge things like the age of Big Boss at the time of the LET project, the hair colour of specific characters certainly is open to being changed at the drop of a hat to fit any new story beat required.
As with many things, they retconned it -- or, simply kept him with his iconic brunette look throughout the rest of the series. It isn't worth over thinking, honestly.
But, it makes more sense for a young Solid Snake to meet Big Boss than a young Liquid.