White:
Shiroi
しろい (白い)
Black:
Kuroi
くろい (黒い)
Red:
Akai
あかい (赤い)
Blue:
Aoi
あおい (青い)
Brown:
Chairo
ちゃいろ(茶色)
Yellow:
Kiniro
きんいろ (金色)
Purple:
Murasakiiro
むらさき色
Green:
Midori-iro
みどり (緑色)
Pink:
Pinku-iro
ピンク色
Orange:
Orenji-iro
オレンジ色
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Note:
The other colors besides the primary ones uses Katakana and is mostly the same as the English word like orange and pink.
If you have any other colors you want me to add, just tell me in the comments, I'll be happy to do so.