What is the hex code for Blue?

Blue is #0000ff. In CSS the keyword blue, the hex #0000ff, rgb(0, 0, 255) and hsl(240, 100%, 50%) all paint the same color.

What is the opposite of Blue on the color wheel?

The opposite (complementary) color is #ffff00, the same saturation and lightness rotated 180° around the HSL wheel. Complementary pairs give the strongest contrast, which is why the complement should be used sparingly rather than at equal weight.

Can I use Blue for text?

Blue as text on white has a contrast ratio of 8.59:1, which passes WCAG AA for body text (4.5:1). On black it is 2.44:1, which fails for body text. It works as a text color on light surfaces.

CSS color names · Blues

Blue color: hex #0000ff, RGB and HSL

Blue is the CSS keyword blue, hex #0000ff, rgb(0, 0, 255), hsl(240, 100%, 50%). It is a medium, fully saturated blue in the blues family. Below: the colors that go with it, its tints and shades, how it reads as text, and a complete interface palette built from it.

CSS name: blue
Hex: #0000ff
RGB: rgb(0, 0, 255)
HSL: hsl(240, 100%, 50%)
On white: 8.59:1 — passes AA for body text
On black: 2.44:1 — fails AA; use as a fill, not text

.example {
  color: blue;          /* keyword */
  color: #0000ff;          /* hex */
  color: rgb(0, 0, 255); /* rgb */
  color: hsl(240, 100%, 50%); /* hsl */
}

What colors go with blue

Each match keeps blue's saturation and lightness and rotates only the hue, so the relationship is the wheel's and nothing else. Any of these can be an accent beside blue as the primary; the harmony guides explain which rule suits which interface.

Complementary

The opposite hue, 180° away — the strongest contrast, best kept to one accent per screen.

#ffff00 · yellow

Split-complementary

The two neighbors of the complement, at 150° and 210° — most of the contrast with less tension, and two accents instead of one.

#ff8000

#80ff00

Triadic

Two hues at 120° and 240° — three evenly spaced signals, the scheme charts and category colors want.

#ff0000 · red #00ff00 · lime

Analogous

The neighbors at −30° and +30° — calm and cohesive, with emphasis coming from weight and size rather than hue.

#0080ff

#8000ff

Tints and shades of blue

Tints add lightness toward white; shades remove it toward black. The hue and saturation stay fixed, so every step still reads as blue — these are the hover, pressed, disabled and surface variants a single brand color needs.

Tints (lighter)

#2b2bff

#5555ff

#8080ff

#aaaaff

#d4d4ff

Shades (darker)

#0000d4

#0000aa

#000080 · navy

#000055

#00002b

A UI color palette built from blue

The eight semantic roles an interface actually uses, derived from blue as the primary with the split-complementary rule: secondary and accent rotate around the wheel, and the five neutrals take the hue at lightness steps tuned for light and dark mode. This is the same derivation the palette generator runs — open it there to change the rule, drag the anchors, or export the set as CSS variables.

Light mode

primary: #0000ff
secondary: #ff8000
accent: #80ff00
background: #fcfcfd
surface: #f3f3f7
text: #111122
muted: #56568f
border: #dfdfec

Dark mode

primary: #1a1aff
secondary: #ff8c1a
accent: #8cff1a
background: #0e0e1b
surface: #151528
text: #f3f3f6
muted: #9494b8
border: #272749

Open blue in the palette generator

Using blue in an interface

Blue is the default interface color for a reason: it sits comfortably behind content, it has a wide usable lightness range for hover and pressed states, and its complement (orange) leaves red and green free for status. Most of the good primaries in this set are here. Whichever role blue takes, define it once as a token rather than repeating the keyword: the semantic palette guide covers the eight roles, and the guides to complementary, triadic and the other color schemes explain how to weight the matches above.

What is the hex code for Blue?: Blue is #0000ff. In CSS the keyword blue, the hex #0000ff, rgb(0, 0, 255) and hsl(240, 100%, 50%) all paint the same color.
What colors go with Blue?: Its complement is #ffff00, the split-complementary pair is #ff8000 and #80ff00, the triadic partners are #ff0000 and #00ff00, and the analogous neighbors are #0080ff and #8000ff. In an interface, use Blue for most colored elements and one of these for a single accent, at roughly an 80/20 split.
What is the opposite of Blue on the color wheel?: The opposite (complementary) color is #ffff00, the same saturation and lightness rotated 180° around the HSL wheel. Complementary pairs give the strongest contrast, which is why the complement should be used sparingly rather than at equal weight.
Can I use Blue for text?: Blue as text on white has a contrast ratio of 8.59:1, which passes WCAG AA for body text (4.5:1). On black it is 2.44:1, which fails for body text. It works as a text color on light surfaces.