Visual Design
Alpha (Transparency)
Alpha is the transparency component of a color, separate from its hue. Full alpha is fully opaque, while lower alpha lets the surface behind show through.
Why it matters
Transparency lets elements blend with their surroundings instead of sitting as hard blocks. Understanding alpha helps explain why some overlays feel airy and others feel heavy.
In depth
Alpha is the fourth value in color formats like RGBA, where it controls opacity from transparent to solid. A color with reduced alpha recedes into whatever sits beneath it, picking up that background, while a solid color sits firmly on top. This is useful for subtle borders, shadows, and overlays, since a translucent layer adapts to different backgrounds more gracefully than a fixed color.
Real-world example
A dark overlay behind a popup is often a semi-transparent black, dimming the page beneath without hiding it completely.
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