There are several misconceptions about noise gates being bandied round here.

If a noise gate is coloring your sound you either:
a) have a broken noise gate or
b) haven't set it up properly

A noise gate is in essence like an automatic no/off switch. You key in the threshold value which triggers upward expanders / downwards expanding filters to kill the signal. These should not be active when you are playing if they are you have your threshold set too high. Think of the threshold like an upside down compressor. A compressor kicks in when the signal level raises above a certain value and it applies a user defined level of compression. A noise gate looks for signal dropping below a predefined level and then wipes it out to kill buzz and humm.

Clipping results for having your threshold set too high