Inspect Chartreuse (#7FFF00) in HEX, RGB, HSL, LCH and OKLCH, check its contrast, and copy the value you need.
Chartreuse
#7FFF00
Black text reads best on this background, at 16.21:1.
Chartreuse is one of the 148 CSS named colors, and resolves to #7FFF00 in every browser. In numbers that is rgb(127, 255, 0) and hsl(90, 100%, 50%). Perceptually it is a very light, vivid color: OKLCH puts its lightness at 89% and its chroma at 0.265. It sits in the greens at 136 degrees of OKLCH hue, and reads as a cool color.
White text only reaches 1.3:1 here, so black text is the safer pairing at 16.21:1. Because it is this light, Chartreuse works best as a page or card background with dark text over it.
The closest CSS named colors to Chartreuse, measured with CIEDE2000, are LawnGreen (#7CFC00), GreenYellow (#ADFF2F), Lime (#00FF00). If Chartreuse is not quite right, those are the nearest keywords to try before reaching for a custom value.
HEX
#7FFF00
RGB
rgb(127, 255, 0)
HSL
hsl(90, 100%, 50%)
HWB
hwb(90 0% 0%)
CMYK
cmyk(50%, 0%, 100%, 0%)
LAB
lab(90.05 -61.49 83.86)
LCH
lch(90.05 103.98 126.25)
OKLCH
oklch(89.03% 0.2648 136.01)
WCAG asks for 4.5:1 between body text and its background. On #7FFF00 white text measures 1.3:1 and black text 16.21:1, so black clears it and white does not.
White text on Chartreuse
WCAG 2.2
1.3:1
APCA
Lc 16
Fails AA body text
Fails AAA body text
Fails AA large text
Black text on Chartreuse
WCAG 2.2
16.21:1
APCA
Lc 89
Passes AA body text
Passes AAA body text
Passes AA large text
Check Chartreuse against any other color in the contrast checker.
Chartreuse sits at 89% OKLCH lightness. Holding its hue and chroma and moving only that value carries it up to #EDFFE5 and down to #020800, which keeps the family recognizable instead of letting it drift toward gray the way a plain HSL ramp does.
#9CFF66
20% lighter
#B4FF90
40% lighter
#C9FFB0
60% lighter
#DCFFCC
80% lighter
#EDFFE5
100% lighter
#61C600
20% darker
#459000
40% darker
#2A5E00
60% darker
#123000
80% darker
#020800
100% darker
Build a full accessible scale from #7FFF00 in the shade generator.
Hues rotated around #7FFF00 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.
Chartreuse sits at 136 degrees. Rotating it a half turn lands on 316 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 Chartreuse at 106 and 166 degrees. They stay close enough to read as the same family, which is what you want for hover states, secondary surfaces and gradients.
136, 256 and 16 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 316 degrees, this pair flanks it at 286 and 346. You keep most of the contrast of a complementary pairing while losing the harshness.
Explore more combinations around Chartreuse on the color wheel.
The biggest shift is under achromatopsia, where #7FFF00 reads as #D1D1D1, 31.9 CIEDE2000 units away. If Chartreuse is the only thing marking a state or a series, roughly one viewer in twelve will miss it.
Protanopia
#FFD700
Deuteranopia
#FFCF09
Tritanopia
#8CE3B1
Achromatopsia
#D1D1D1
The nearest CSS keywords to #7FFF00, ranked by perceptual distance rather than by how close their hex digits happen to look.