Inspect AliceBlue (#F0F8FF) in HEX, RGB, HSL, LCH and OKLCH, check its contrast, and copy the value you need.
AliceBlue
#F0F8FF
Black text reads best on this background, at 19.58:1.
AliceBlue is one of the 148 CSS named colors, and resolves to #F0F8FF in every browser. In numbers that is rgb(240, 248, 255) and hsl(208, 100%, 97%). Perceptually it is a very light, near-neutral color: OKLCH puts its lightness at 98% and its chroma at 0.013. It carries almost no chroma, so it behaves as a neutral rather than as a hue, and belongs with the off-whites.
White text only reaches 1.07:1 here, so black text is the safer pairing at 19.58:1. Because it is this light, AliceBlue works best as a page or card background with dark text over it.
The closest CSS named colors to AliceBlue, measured with CIEDE2000, are GhostWhite (#F8F8FF), WhiteSmoke (#F5F5F5), White (#FFFFFF). If AliceBlue is not quite right, those are the nearest keywords to try before reaching for a custom value.
HEX
#F0F8FF
RGB
rgb(240, 248, 255)
HSL
hsl(208, 100%, 97%)
HWB
hwb(208 94% 0%)
CMYK
cmyk(6%, 3%, 0%, 0%)
LAB
lab(97.12 -1.77 -4.33)
LCH
lch(97.12 4.68 247.74)
OKLCH
oklch(97.51% 0.0127 244.25)
WCAG asks for 4.5:1 between body text and its background. On #F0F8FF white text measures 1.07:1 and black text 19.58:1, so black clears it and white does not.
White text on AliceBlue
WCAG 2.2
1.07:1
APCA
Lc 0
Fails AA body text
Fails AAA body text
Fails AA large text
Black text on AliceBlue
WCAG 2.2
19.58:1
APCA
Lc 101
Passes AA body text
Passes AAA body text
Passes AA large text
Check AliceBlue against any other color in the contrast checker.
AliceBlue sits at 98% OKLCH lightness. Holding its hue and chroma and moving only that value carries it down to #03060A, which keeps the family recognizable instead of letting it drift toward gray the way a plain HSL ramp does.
#B8C0C7
20% darker
#848B91
40% darker
#535A5F
60% darker
#262C32
80% darker
#03060A
100% darker
Build a full accessible scale from #F0F8FF in the shade generator.
The biggest shift is under tritanopia, where #F0F8FF reads as #EDFAFA, 4.6 CIEDE2000 units away. If AliceBlue is the only thing marking a state or a series, roughly one viewer in twelve will miss it.
Protanopia
#F5F8FF
Deuteranopia
#F3F6FF
Tritanopia
#EDFAFA
Achromatopsia
#F7F7F7
The nearest CSS keywords to #F0F8FF, ranked by perceptual distance rather than by how close their hex digits happen to look.