I think Topper's right on the money. A lightbulb would have shone too bright and left a "halo" around the eyes, particularly with the pre-digital video camera technology of the early 70s.
The "reflective glass beads" is far more likely, although I have personally never seen that in a paint form. I have used a self-adhesive vinyl film commercially known as "Scotchlite" which is commonly used to make reflective signs, such as street marker signs. It is a thin sheet of vinyl impregnated with glass beads, and then laid over with another sheet of vinyl, either clear or colored. This is also how they mark school buses, ambulances, and other emergency vehicles for safety.
In the Richard Donner Superman movie the citizens of Krypton had glowing costumes that were made with a glass bead-impregnated fabric. They used directional lighting from the front of the camera which gave them the effect of glowing. If you were to see them with the light turned off they would appear as black. But with the light on they were a radiant blue-white. You can see this demonstrated on the Superman DVD.
If you were to want to experiment with Scotchlite you might ask a local sign shop for assistance, but be warned, it is not cheap! it also would not work very well for a live production, as the reflection is very directional and would not work from all angles in an audience. For camera use, however, it would work very well.