After a few years and with a preservative oil the gray phosphate will turn sort of like an olive drab green color.
All the parts I had phosphate back in the mid-80's and preserved with oil, today look more like that green. Also, the metal composition will also have an impact on the shade it comes out after phosphate. My bolts are a darker gray while the throttle linkage treated in the same batch as the bolts came out more like the OD green I mentioned.
Mike