RGBA color values are an extension of RGB color values with an alpha channel - which specifies the opacity for a color. An RGBA color value is specified with: rgba(red, green, blue, alpha). The alpha parameter is a number between 0.0 (fully transparent) and 1.0 (fully opaque).

Green, orange, yellow, and blue — each of these is a hue, a color or a shade that's true. A rainbow shows the melting of one hue into another, from red to violet, and all shades in between. The noun hue means both a color and a shade of a color.

Color saturation refers to how vivid, rich, or intense a color is. It is one of the three elements of color, with the other two being hue and value.

HLS color model A color model that defines colors by the three parameters hue (H), lightness (L), and saturation (S). It was introduced by Tektronix Inc. Hue lies on a circle, saturation increases from center to edge of this circle, lightness goes from black to white. This model uses the same hue plane as the HSV model, but it replaces value (V) by an extended lightness axis so that the maximum color gamut is at L=0.5 and decreases in each direction towards white (L=1) and black (L=0). The HLS color model is represented by a double hexagonal cone, with white at the top apex and black at the bottom.

Color gradients, or color transitions, are defined as a gradual blending from one color to another. This blending can occur between colors of the same tone (from light blue to navy blue), colors of two different tones (from blue to yellow), or even between more than two colors (from blue to purple to red to orange).

amber – between brown and yellow in colour. amethyst – light purple. avocado – with a pale green colour. azure – bright blue.