"I wear a white shirt."
Thank you for your frank comment. I try to explain it again. I had played the competition using kanji with classmates when I was an elementary school student. We make different kanji by adding stlokes to original kanji. The start is a simple kanji if possible. The winner is the person who wrote the most kanji.
this is an old comment, but the thread hasn't addressed this yet, so! for anyone who might have this same question! しろ/白 on its own does mean "white," but it's actually a noun, not an adjective. adding い to the end makes it what is called an "い adjective," one of three types of Japanese adjectives. once it's an adjective, you can stick it in front of another noun to describe it, just as you can in English: 白いシャツ。you could not write simply 白シャツ; that would be incorrect.
(there is actually a way to make the noun 白 act like an adjective without adding the い, which is to put の in between it and the noun it's describing: 白のシャツ. this is something you can do with all nouns to turn them into makeshift adjectives in Japanese. for the purpose of this lesson, though, just remember that 白 on its own is the noun "white" and 白い is the adjective "white.")