Color systems
Choose the behavior that caused the problem. These ten guides include complete examples, clear input limits and sources; eight CSS demonstrations run locally in your browser.
Keep an opaque label clear, or make borders and an inline geometric icon follow the component foreground.
Use alpha on the background when only the panel surface should fade. The opacity property composites the whole element, including its descendants; a child set to opacity:1 does not cancel its parent’s group opacity.
Set the component’s foreground color once, then use currentColor where a border or inline icon should follow it. currentColor resolves from the color property on that same element, so an icon with its own color can legitimately differ from the label.
Separate alpha bytes, authored spellings, numeric precision and the color space returned by a browser.
CSS eight-digit HEX uses #RRGGBBAA: alpha comes last. Four-digit HEX repeats each nibble to make the eight-digit form. Divide the alpha byte by 255; an alpha byte of 80 is about 0.5019607843, so it is close to, but not exactly, a 50% alpha value.
A browser can return an rgb() string for a color authored as HEX, a name or HSL without changing the intended color. Keep the source declaration separate from the computed result, and compare values in their stated color space rather than treating different strings as automatic failures.
Use the existing supported alpha and gradient models for different background conditions.
Use the stated single-backdrop alpha model and calculator; keep group opacity outside its scope.
Check the conditions and intermediate samples instead of treating two endpoint results as a whole-background guarantee.
Compare equal HSL lightness on explicit backdrops and understand why HWB can lose its hue.
HSL lightness describes a color coordinate, not its contrast against a reading surface. Equal-lightness yellow and blue can have very different sRGB relative luminance and white-background contrast.
When HWB whiteness and blackness sum to 100% or more, the result is achromatic. Divide whiteness by their sum to get the gray level; changing hue cannot restore color in that condition.
Keep normalized proportions, final alpha, accepted CSS syntax and reported output gamut separate.
color-mix() normalizes its weights before mixing. When explicit weights sum to less than 100%, the remaining share also reduces final alpha; the base blend and its opacity are separate results.
CSS syntax support and a reported screen gamut answer different questions. Keep an intentional sRGB fallback, use feature queries for accepted syntax, and treat color-gamut as an approximate output capability signal.
A valid CSS token, matching inherited colors and a useful contrast calculation answer different questions. Keep the alpha layer, backdrop, color space and supported inputs visible when moving between guides. These examples do not certify an entire interface or measure a physical display.