I'm guessing this is to be used for a patio?

Possible it may change the color. Travertine is in the limestone family which is a very soft stone. Too strong a solution may damage or at the very least make it rough.

Most travertine is honed for a smooth finish. I don't use here in the northeast as I have seen cracks from freeze/thaw conditions that's dry laid. Also, the stone is generally only 1" thick and is not suitable in my opinion for patios.

We did however use it on an indoor pool patio where it was set in mortar and it came out beautiful. This would be the only exception in my area.

I would try a test piece prior to committing to the full blown acid wash.

I had them do one piece acid washed and its so much darker. I love the look of the natural stone so acid wash is def not an option for me now. Thanks for your feedback.