Phil has had many different tones over the years, and each tone tends to work only in context. I played in Dead bands back in the 80s, and just got back into it a few years ago. I find that both the tones I can use and the aspects of Phil's playing, such as I'm capable of, only work in certain places. One of the hallmarks of his tone has always tended to be the cutting of frequencies for a "tighter" sound. He likes to be loud and up front, but there are only so many frequencies that aren't already being taken in a band with 2 guitarists, keys, and usually 2 drummers. Those available frequencies morphed over time in the bands he played with, and so his tone changed as well. Similarly, a line he would play in 1968 might not have fit in 1977 or 1989. As with any improvisational music, it's all about what fits with the rest of the music.
As for his playing style, he has always mixed very short staccato notes with longer ones, and plays melodic lines that reflect his background as a horn player (phrasing and "function" in the music) and a composition student (long lines that have an internal logic to them rather than just short licks or phrases).
I'm really interested to hear some of the other folks who play in Dead bands. Every "Jerry" seems to gravitate toward certain aspects of his playing, but Phil's playing can be so mysterious (he does a lot of stuff that makes me say "that worked, but I have no idea why, and I doubt I could have made that work") that I'm really curious to hear what other folks are doing.
Here's a clip of my band (albeit a few personnel changes ago):