The use of the term khaki was used informally and interchangeably with the more often used terms drab or olive drab, which in the U.S. Army was first applied to unbleached duck material used for field equipment. The term "Khaki" for uniform and field equipment began to be used around 1900 and I believe was probably picked up from the British troops that the U.S. operated with during the China Relief Expedition 1900.
The more common term "Drab" used in most correspondence of the period 1873 to 1900 and "Olive Drab" after 1900 were used interchangeably, with khaki thrown in once in awhile (especially in official U.S. Marine Corps correspondence). The more green shade of color usually referred to as "olive green" for web equipment was officially adopted in 1907. Problems with obtaining suitable dyes delayed acquisition of materials in olive drab until 1909.
At the time the Hoff first aid pouch and field dressing was adopted the standard color of woven and duck fabric field equipment was olive drab, and all of the Hoff first aid pouches I have examined were olive drab (or khaki if you prefer).
After the olive green material began to be used for web and fabric material the primary manufacturers of field equipment, Rock Island Arsenal, and Mills Woven Cartridge Belt Co. produced both drab and olive green equipment. Rock Island Arsenal apparently concurrently produced drab equipment for issue to the militia, and olive green equipment to be issued to the Regular Army. Mills manufactured most of their field equipment on contract and commercial sales in olive green until 1917.
The dyes for the olive green web and duck materials was obtained from Germany and was no longer imported after the declaration of war in April 1917, and the Army reverted to drab for field equipment.
For a more direct answer to your question the blue equipment was obsolete by the time the Hoff first aid pouch was adopted.