Ah, you know what. The switch is black. I'm at work, so I forget.Lets see a photo of the dash please. I can't remember any yellow switch other than the one that toggles through the display modes. I think turf mode is handled through the AWD switch on the throttle housing.
The switch by the throttle is 2wd to AWD.
But this is what I was referring to (not my pic):
On mine the picture is blank. Must be worn out. Its just a blank switch. But this pic shows it as a light. So I guess that's what its for.