Yes, khaki is a color, even if not one of the primary colors, in the
same way peach, maple and aquamarine are colors. I found two web pages
with the history of khaki.
Khaki - comes from Urdu language, 'khak' meaning earth- or dust-colored.
From Wikipedia, the free encyclopedia
The First Foot Guards - You can blame Brigadier Harry Lumsden for khaki
- Explains how khaki was first used by the west.
To see some contemporary usage, here is khaki in a color chart:
Color Chart for Web Page Development - www.BROBSTSYSTEMS.com
Google search terms used:
khaki color chart
I hope this has been a most helpful answer. If you need anything else,
or have a problem with the answer, do please post a Request for
Clarification before rating and I shall respond as soon as I can.