[gremlin]

Yes, I know it is meant to turn orange eventually, but surely not yet? 
 
It is an Atlantic Giant that has been the expected straw colour so far, but suddenly changed colour this week. It's about football sized, so pretty pathetic really.

Does this mean that it will stop expanding as the skin ripens, and if I continue to feed and water it it might split or even explode     

There are almost 8 weeks till the competition weigh in, so I will need to keep it going till then.

[Yana]

I don't know about Atlantic Giant Gremlin, but my Jack O'Lanterns are orange already and don't seem to be getting any bigger, but I'm not the expert. 

[wil4025]

Mine have all gone orange this week. Im sure they might add more growth if you keep feeding it. Im no expert as this is my first successful year with some big ones.

[polly nator]

My Mars all started going orange last week and are now well on their way. They had stopped expanding some time before that.  I shouldnt worry. Better to ripen than not ripen!  And they will store.

[rowan57]

Keep them on the vine for as long as possible, they will even take a very light grass frost (but letting them get this far is risky, as if its much more than that they could be damaged). This will ensure that they are fully ripe and as sweet as possible.

[gremlin]

Thanks for the replies.   I have other squash for eating and we wont have any shortage.
   
It is the first year I have tried growing a pumpkin purely for size and for fun.  It might make a Halloween lantern..... then it is compost.  I will probably try saving seed for next year although I don't know what flower pollinated it and I could get anything.

I haven't been able to find anything much on the internet about pumpkin ripening although there might be a suggestion that the skin takes about a month to fully harden.  It might need warmth AND sunshine, but I don't know which is more important.  It is is mostly sunshine for example I could try putting a black  bag over it.

A lot of the fun in gardening for me is finding out how to grow new stuff.  It has taken me three years to learn how to grow cucumbers, although it might not be me....just the good weather this summer.