I last had an email conversation with Alex from Haveston on the 20th of September regarding new colours for the Canvas and Parade ranges, and I believe at that time the colours you mention were already available as you'll find photographs of these straps on customers watches on the Haveston Facebook page before this date. His comment then was that . . .
"Our next Canvas and Parade colours have actually been placed on hold, as we are developing new strap types with our material suppliers and makers. However in brief, we have been looking at various printed canvas references from historical use. Regarding the next Parade tones they will likely be Grey and Military Olive Drab (Green), but as mentioned will be scheduled for later."
I'm on their mailing list and so far I've had no word about any new developments. It's the Parade I'm interested in for my Damaskos due to it's thinner material, and I'm not convinced that canvas as a strap material will retain it's looks and colour after being worn 24/7 for 2 or 3 weeks on a watch in rotation, and washed every few days.