A1 was an Alhambra, Calif. based manufacturer who produces traffic signal related equipment. They are fairly popular for things such as hardware / mounting brackets, however for a period (I believe mostly the 1970s) produced a line of signal heads such as the one you’ve mentioned. Their heads are exclusive to California and are desired by collectors, especially if they have diamond-print glass lenses.
If the signal is incandescent with glass lenses, the green indication will have a blue hue went not lit. This was standard with most manufacturers in the US, and will appear the usual green when lit. Paint wise, most of their equipment was painted a dark olive green which tends to patina with age, unless the city repainted it.
For more technical details,I’d suggest viewing the signal collector-supported
HighwayDivides.net Wiki page:
See Here Hope this was of help.