I saw the photo, and I would still guess they are low point drains for the hot-cold water lines. Unfortunately they did not color code them for you. On my rig (only one year newer than yours), one is red and one is blue (hot and cold).
Through previous discussion on this forum, it is apparent that no two models are the same (as far as construction practices go), and some models may not have a fresh water tank drain if I recall.
On my coach, the fresh water tank drain looks like this:
Which is the most common configuration. However, some coaches do use a different valve for the tank water drain, which looks closer to yours.
The definitive answer would be if you can locate your fresh water tank. If it has a drain, it's water line should be directly attached to the tank. If you can find it, perhaps you can follow it's general direction and perhaps locate the drain.
On the other hand, if you cannot find the water line, then you likely don't have a drain connected directly to the tank.
You should have 4 lines connected to your fresh water tank; the fill, the fill vent, the water line going to the water pump, and a drain line (if you have one).