I always check for bed bugs and have noticed that there are 2 different mattresses at Hilton Hotels. The newer one is whiter in color and a bit firm. The older mattress is more comfortable and is more of a beige-white color, somewhat yellow. I'm not sure when the change happened, but as properties renovate they seem to be switching to the whiter, firmer mattress.

I did see a third mattress but only at one hotel - Hilton Tampa Downtown, it was by far the most comfortable of the three, and one of the most comfortable mattresses I've seen in a hotel.