Yep the Glide cards at the time the game was released didn't have 32bit modes, only 16 bit.
The only Glide cards to offer 32bit color depth was the Voodoo5. I don't know if this game could detect voodoo 5 and allow the switch to 32 bit mode.
I'm not sure if any of the current wrappers even emulate Voodoo5. Some have limited Voodoo 3 modes (don't remember the difference over older Voodoo cards except maybe extra memory and speed?).
GaminggUy45: Does 32bit color only work in DirectX? because it doesn't seem to be working in 3DFX for me after selecting it.
BatJoe: As others have said yes, only in Direct mode. You should be able to switch to it easily enough.
Keep in mind that not playing 3dfx, you lose several graphical special effects in the game that Unreal engine glide support allowed for.