The genuine VT100 has a white phosphor IIRC, but the
VT640 I
say had a green phosphor CRT fitted.
All the DEC CRT terminals were available with customers choice of green, white, or amber
CRT's. Probably some other phosphors I didn't see too.
The default phosphor was white for the VT100. My distant memory tells me that VT100-LC was
the order code for the green phosphor I liked best (P31, long glow?).
By the time of the VT-220, amber was really popular.
Tim.