Add more color transformation functions & fix `color.invert`

The color.invert function doesn't modify the colour. In addition, I'd love to see some extra functions for manipulating colours!

`color.hue.set(color, hue)`

Sets the color's hue with the HSV color model, preserving the saturation and value of the provided color. Hue is a value between 0 and 100.

`color.hue.get(color)`

Gets the color's hue, between 0 and 100.

`color.hue.shift(color, hue)`

Offsets the color's hue with the HSV color model. Hue is a value between 0 and 100. Will wrap values that are out of bounds.

`color.saturation.set(color, saturation)`

Sets the color's saturation with the HSV color model, preserving the hue and value of the provided color. Saturation is a value between 0 and 100.

`color.saturation.get(color)`

Gets the color's saturation, between 0 and 100.

`color.saturation.shift(color, saturation)`

Offsets the color's saturation with the HSV color model. Saturation is a value between 0 and 100. Will clamp values that are out of bounds. Note: This is very similar to the color.dark & color.light functions, which I believe should/could be aliased to color.darken & color.lighten as these names are clearer.

`color.value.set(color, value)`

Sets the color's value with the HSV color model, preserving the hue and saturation of the provided color. Value is a value between 0 and 100.

`color.value.get(color)`

Gets the color's value, between 0 and 100.

`color.value.shift(color, value)`

Offsets the color's value with the HSV color model. Value is a value between 0 and 100. Will clamp values that are out of bounds.

`color.lerp(a, b, amount)`

Mixes the two colors by lerping their RGB components by amount. Amount is a value between 0 and 100.

`color.add(a, b)`

Combines the two colors by adding their individual components. Opacity is not modified.

`color.multiply(a, b)`

Combines the two colors by multiplying their individual components. Opacity is not modified.

Also, as an extra ask, something rarely implemented in other tools: CIELAB color functions. This is an extremely useful color model, particularly as it can provide consistent preceived lightness between different hues and chrominance (color intensity).

Here's the sort of thing I have in mind:

color.lab.lightness.[set|get]
color.lab.chroma.[set|get]
color.lab.hue.[set|get]

See: Color Picker & Code

moudey / Shell