You can create channel letter signs that allow the customer to select front-lit and back-lit colour options.
How to enable the glow for front-lit channel letter signs
Navigate to the admin of Sign Customiser on your store.
Click on "Customisers" in the home menu
Click on the customiser you wish to edit
Click on "letter types"
Click on the letter type you wish to edit
Click on the "Face" option
Scroll down until you see the card titled "Face / Front Lit Settings"
Make sure "Acts as light source (Enable Front lit)"
How to create back-lit channel letter signs
Navigate to the admin of Sign Customiser on your store.
Click on "Customisers" in the home menu
Click on the customiser you wish to edit
Click on "letter types"
Click on the letter type you wish to edit
In the card title "Letter parts" make sure you have option "Back lit" switched to active
Click on the "Back lit" option to begin adding colors to it.