Red
い adjective
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of red? Why, it's red!
This has the same reading as the kanji you learned, meaning you know the reading!
赤いネクタイを下さい。
Please give me a red tie.
今、赤いマニキュアが人気ですよ。
Red nail polish is popular right now.
このトマト、今日赤くなったばかりなんです。
This tomato just turned red today.