It's a scheduled maintenance light. blinks at certain hour intervals. reminds users for oil changes, grease things and such. see how many hours you have on the machine and check the book. it'll tell you what's due at that hour marking.
Wow I should probably read my manual a little better! I have an 825 so it might be a little different, but it looks like I'm wrong! (yeah I said it, my wife would be proud) Looking at the instrument panel picture they have that wrench/book on the far left of the display and noted with this:
"-System Diagnostic Light (Gas Engine Models Only)
-This light will illuminate for up to 4 seconds when ignition key switch is turned to the RUN position. The light will illuminate when sensors malfunction. If light is on, stop machine and shut off engine. If light is active after restart, contact you John Deere dealer."
I am confused a bit tho since you say yours is blinking. Is it blinking constantly or just at start up or even just blinking a certain number of times....?
I just immediately assumed it was like my tractor and blinked to say "hey dipthong, change my oil and check me out, I got 50 hours on me!".
Hope it helps, but I would just call or stop in at the dealer and nicely ask at random. Or even google it. (not quite the most accurate method tho) Mostly the guys at my dealership will just tell me, if they know, rather than having me bring it in for service, but everybody's different...