I thought red was 빨간?
If you read the notes available on the full website for the color bundle of lessons, you'll note that form above is the noun form of the color.
Which one is the noun form of the color? 빨간 or 빨강?
So 빨간(색인) is the adjective form?
use 빨강 or 빨간색 or 빨간 something