Applies a transparent color to the outlines. The outlines will still take up the space defined by the outline-width value.

You can use one of the 140+ color names.

You can use hexadecimal color codes.

You can use rgb() color codes:

• the first value is for red
• the second value is for green
• the third value is for blue

Each of them can have a value between 0 and 255.

You can use rgba() color codes:

• the first 3 values are for rgb
• the 4th value is for the alpha channel and defines the opacity of the color

The alpha value can go from zero 0 (transparent) to one 1 (opaque).

You can use hsl() color codes:

• the first value is for hue and can go from 0 to 359
• the second value is for saturation and go from 0% to 100%
• the third value is for luminosity and go from 0% to 100%

You can use hsl()a color codes:

• the first 3 values are for hsl
• the 4th value is for the alpha channel and defines the opacity of the color

The alpha value can go from zero 0 (transparent) to one 1 (opaque).