Assigning different colors to queues is a great way to differentiate between them visually.
Here is how you can change the color of a Queue once it has been setup:
Click on the Menu Button and select Queue Manager.
Select the Queue you wish to alter. This will open the Queue Settings window, specific for the one you selected.
The third setting is called Queue Representation Color. It has a Color Swatch showing you the selected color as well as a hexadecimal RGB value for that color (each digit pair representing either Red, Green, or Blue.)
Click on either the swatch or RGB value. This will open a color color selection window.
Since computers nowadays are able to display 16.7 million colors, it is impossible to show a windows with all those colors at once.
Instead, the color selection window has a color spectrum bar on the right side. Pick a color region of the spectrum and then select a more specific hue out of that region from the left side of the window.
The Queue's color is updated on the fly.
Click on the Color Swatch or RGB value to close the color selection window.