I'll readily admit my lighting wasn't optimal; looking at my Bumblebee right now, his yellow is a bit darker than most of my photos. A different camera could also affect how he looks in a photo.
In comparing the figure to the Camaro used in the 2007 movie, it doesn't help that the colour of the car changes depending on the lighting and the shot. In some photos it has an orange tint to it, in others it looks metallic, like a bright gold.
It's unknown how specific the licensor - Chevrolet - is with Bumblebee's colours. Hasbro have had more than a few shades of yellow with Bumblebees over the years. That and the black and grey repaints (and 2007's Cliffjumper) seem to imply that Chevrolet aren't too fussy with the colours.