Summary:
The Cyrillic capital letter "Ч" makes the line of glowing text (outline) gray. Other letters/symbols have no problems (I checked all the letters that are on the keyboard - only Cyrillic letters). The small letter "ч" has no problem. Note: for dyed signs, the outline becomes the corresponding correct color.

Steps to reproduce:

1. Place the sign.
2. Write/paste the letter "Ч" (you can also add other letters).
3. Take the Glow Ink Sac and make the text glow.

Observed results:
The line containing the letter "Ч" has a gray outline.

Expected results:
The line containing the letter "Ч" will have a white outline.

Screenshots: