Automatic Electric sold equipment to a variety of "independent" telephone companies, not just GTE.
Anyway, Western Electric did make beige and green pay phones.
It's pretty easy to spot an AE vs WE telephone set: Western Electric phones have the finger spot at the 3 o'clock position while AE phones have it at the 5 o'clock position.[TELECOM Digest Editor's Note: Plus which, on (at least the older) AE rotary dial phones, the dial would return 'faster' when you removed your finger. WE dials pulsed and clicked their way back. PAT]