Advantages of a tube CD player over an SS player?

tube cd player has tube buffer stage that pleasantly colors signal while one without tube buffer sounds newtral and more accurate.

There are too many variables involved to form any stereotypical opinions. There are "colored" tube players and there are exceptionally honest and pure sounding tube players. SS players can be colored just as much, just in a different direction/characteristics. I've heard excellent examples of both and poor versions of either. I'd focus on quality of analog circuit, power supply and designer talent/ implementation. In my experience tube-transistor differences seem less with digital sources than with amplifying components.
Charles,

tube cd player has extra tube buffer. the rest of hardware is just like in ordinary cd player. extra buffer implies to extra circuit elements implies to extra stage in the signal path implies extra colorations.
you can make any cd player with tube output stage. just purchase musical fidelity tube buffer and even pocket cd-player can become tube cd-player.

All things being equal, and they never are, especially the DAC chip, tubes should sound better.