There is a 50 watt coated HPS lamp in a can light at my work. This light is left on 24/7 and the lamp is a year old.  Within the past couple of weeks I have noticed some odd color shifting when the lamp is on. Due to it being coated, it gives off a cool white light as opposed to the orange color of streetlights. It sometimes turns a greenish light, but never cycles. After a little while it will shift back to its normal color. Yesterday it turned very orangish and today it was running green again. It shifts several times a day so by the time I pass it one time, it has changed by the enxt time I see it. I have never seen this lamp cycle though, it just changes colors, any thoughts?

It is depleted of sodium, end of life state.
Why it does not cycle: Reason might be electronic ballast (i gues there will be simple HF electronic), what does not depend on height of reignition peaks, as the lamp arc does not extinguish the very fast current zero-cross (compare to magnetic ballast, where the zero-crossing phase take miliseconds, so the arc has to reignite. When reignition peaks are higher then OCV, the lamp goes out, so the cycling)

I've never seen a coated HPS give off cool white light...what you describe sounds more like metal halide, but I could be wrong.

Yeah, it's probably MH, replace it soon or BOOM!  rapid color shift in an MH is the usual sign of a BOOM!