NetLogo 7.0.0-beta2:

palette:with-transparency

color palette:with-transparency number

Reports an RGBA color with an alpha value equivalent to the transparency number and the RGB content of color. An error message results if number is not in the range 0 to 100.

Example:

show red palette:with-transparency 100 ;; [215 50 41 0]

Take me to the full Palette Extension Dictionary