Inspect RoyalBlue (#4169E1) in HEX, RGB, HSL, LCH and OKLCH, check its contrast, and copy the value you need.
RoyalBlue
#4169E1
White text reads best on this background, at 4.85:1.
RoyalBlue is one of the 148 CSS named colors, and resolves to #4169E1 in every browser. In numbers that is rgb(65, 105, 225) and hsl(225, 73%, 57%). Perceptually it is a mid-toned, vivid color: OKLCH puts its lightness at 56% and its chroma at 0.188. It sits in the blues at 266 degrees of OKLCH hue, and reads as a cool color.
White text clears WCAG AA on a RoyalBlue background at 4.85:1. At this chroma it is loud enough to be an accent or a call to action, but it will fight anything else vivid placed next to it.
The closest CSS named colors to RoyalBlue, measured with CIEDE2000, are SlateBlue (#6A5ACD), MediumSlateBlue (#7B68EE), SteelBlue (#4682B4). If RoyalBlue is not quite right, those are the nearest keywords to try before reaching for a custom value.
HEX
#4169E1
RGB
rgb(65, 105, 225)
HSL
hsl(225, 73%, 57%)
HWB
hwb(225 25% 12%)
CMYK
cmyk(71%, 53%, 0%, 12%)
LAB
lab(46.8 17.78 -66.66)
LCH
lch(46.8 68.99 284.94)
OKLCH
oklch(55.98% 0.1882 266.4)
WCAG asks for 4.5:1 between body text and its background. On #4169E1 white text measures 4.85:1 and black text 4.33:1, so white clears it and black does not.
White text on RoyalBlue
WCAG 2.2
4.85:1
APCA
Lc 78
Passes AA body text
Fails AAA body text
Passes AA large text
Black text on RoyalBlue
WCAG 2.2
4.33:1
APCA
Lc 30
Fails AA body text
Fails AAA body text
Passes AA large text
Check RoyalBlue against any other color in the contrast checker.
RoyalBlue sits at 56% OKLCH lightness. Holding its hue and chroma and moving only that value carries it up to #F5F8FF and down to #010025, which keeps the family recognizable instead of letting it drift toward gray the way a plain HSL ramp does.
#5884FE
20% lighter
#7EA3FF
40% lighter
#A6C0FF
60% lighter
#CDDDFF
80% lighter
#F5F8FF
100% lighter
#2A4DC3
20% darker
#1630A5
40% darker
#090C88
60% darker
#030057
80% darker
#010025
100% darker
Build a full accessible scale from #4169E1 in the shade generator.
Hues rotated around #4169E1 in OKLCH, then pulled back into the sRGB gamut. Each swatch is labelled with the nearest CSS named color so you have a keyword to start from.
RoyalBlue sits at 266 degrees. Rotating it a half turn lands on 86 degrees, the hue directly opposite. It is the strongest pairing you can make without changing lightness, and the one most likely to vibrate if you use both at full chroma.
The neighbors of RoyalBlue at 236 and 296 degrees. They stay close enough to read as the same family, which is what you want for hover states, secondary surfaces and gradients.
266, 26 and 146 degrees divide the wheel into thirds. Balanced enough to carry a whole palette without one color dominating the other two.
Instead of the complement at 86 degrees, this pair flanks it at 56 and 116. You keep most of the contrast of a complementary pairing while losing the harshness.
Explore more combinations around RoyalBlue on the color wheel.
The biggest shift is under achromatopsia, where #4169E1 reads as #696969, 27.5 CIEDE2000 units away. If RoyalBlue is the only thing marking a state or a series, roughly one viewer in twelve will miss it.
Protanopia
#4A70E7
Deuteranopia
#3F63DE
Tritanopia
#217E8D
Achromatopsia
#696969
The nearest CSS keywords to #4169E1, ranked by perceptual distance rather than by how close their hex digits happen to look.