Some pumpkins start off yellow while they are forming, but since you say it is a typical seed I doubt you have one of those varieties. Sometimes when fruit are aborting they take on a yellow or slightly orange hue before rotting. I suspect that particular pumpkin didn't make it, a picture would be helpful, but in either case you don't need to do anything other than wait and see. In my garden the bee activity seems to decline around this time of year so you may want to try hand pollinating the next female you see opening.