Travertine is more about texture than it is about wild coloration.
Travertine tile grout color.
This will darken the overall color off the travertine tile but the natural look of the holes will remain and the holes will be filled.
I use custom building products grouts 122 linen would be great product to blend with.
If a matching grout is used it just won t look like travertine.
Other than the meek color it s not for the design faint of heart.
The color travertine you used is a pretty common color.
Unfortunately in this case it sounds like the darker grout did absorb into the travertine tiles and stained the travertine.
Both warm and cool and light and dark shades are found.
More information about this product.
If you re wanting to contrast and go darker as patrick has suggested i would use 59 saddle brown.
This is particularly true for a rougher tumbled finish.
There are many shades of brown available in travertine.
It is advisable to seal travertine tile prior to grouting when using a darker colored grout.
Noce is a travertine with a delightful caramel brown color.
Iranian travertine offers light golden brown and cool light mocha brown.
Grout in a darker color can be chosen to fill the holes and lines for contrast.