Why yellow?

i know that all cats are not the same but the ones ive been around seem to be slow starters,they usually dont range as far out. i have also seen dog aggression out of them. the yellow dogs ive been around seem to start easier and more energetic. the cats that you see now are completely different than the old days they come every color in the book with lots of white.around here they were dark colored dogs with no white and favored a hound in there build,long and lean. now they look like bulldog crosses.