doubt Walter knows Skylar's eye colour.
"What color are my eyes Walt. Tell me. Tell me. You DON'T KNOW do you."
"They're uh uh.."
:: stares at Skylar's sweater, what color would that sweater go with..::
"You're full of shit Walt."
Now was he full of shit because he is wrong or full of shit because she knows that he didn't know but has somehow deduced under pressure the correct answer. Not that it matters because no matter how right he is ultimately she knows he is full of shit and he knows she knows that and on and on for 5 seasons it goes.