I hear this sentiment often, but it doesn't match my own experience with orange cats... the one I had back in high school (orange male) was at least as intelligent as any other cat I've had. The orange female I have now is very clingy / anxious and far more territorial than any of my other cats, but otherwise demonstrates at least average cat intelligence. I'd had a variety of different types of cats - a japanese bobtail, a balinese, a siamese, various calicos and domestic types - and the orange ones have been on the upper end of intelligence by comparison.
My orange boy is not smart. He lets me know when he's hungry by walking over to a house plant and pats at the leaves. Other than that, he's a dumb and lovable guy.
The smartest one that we've had is a Cyprus (looking) cat. She's incredibly athletic, has fantastic spatial awareness, and is a murder-machine if given the opportunity.
