Kai Lord are you by any chance color blind? This is not an insult or anything of the sort, it seems that you are seperating the color from the shape. (It is for this reason that in WWII color blind people were used on bombers, they are more likely to notice patern and shape.)
Judging by shape alone:
Similarities - Both have forward projecting canines, chin barbels, and shovel shaped lower jaws. Unhooded forward facing nostrils, small deeply socketed eyes - again facing forward .
Differences - The large forehead horn, heavier upper jaw, cheek spikes on Blue. Higher forhead and fan like ribbed ears also on Blue.
To me I can see similarities, but the Tarrasque is definetly closer than Blue. (Enough so that I suspect that the rancor was used as a model of sorts.)
The Auld Grump