Mate I had a GPX and I don't remember a 'speed light'

. Having said that mine was a 2000 model...
The only red light I remember is the oil pressure warning (i.e. you're about not have any). Given you're big lad (FWIW I'm a midget) it may be struggling. Check the oil level asap, and maybe even the sender unit.
Welcome to the forum, good to see the older first-time riders in here. I'm 45 in May, only been riding for 8-9 years, wondering wtf I went wrong years ago and wtf I didn't take it up sooner...
...actually I know the answer to that, I was married for twenty years.
I'll have a hunt for the owner's manual for you. To broaden you search criteria you will need to remember the GPX is called a 'Ninja 250R' in the US.
Have a look through here when you have an hour or two to spare:
http://www.ninja250.org/Mick