White hex code

The hex code for white is #FFFFFF. In RGB that is rgb(255, 255, 255) and in HSL it is hsl(0, 0%, 100%).

It has a contrast ratio of 1.00:1 on white and 21.00:1 on black. Body text needs 4.5:1 under WCAG AA, so it works as text on a dark background, not on white.

Its complementary colour, opposite on the colour wheel, is #FFFFFF. Pairing a colour with its complement gives the strongest contrast; for something calmer, use a tint or shade of white instead.

Yes. CSS accepts the keyword white, so color: white and color: #FFFFFF render exactly the same.