Then it's not cat anymore. The purpose of cat is to output the inputs unchanged and concatenated. If you need magic, that's a task for another program.
The terminal emulator does not (and should not, according to my strong opinion) interpret the output of different programs differently.
In fact it's not currently technically possible for a terminal emulator to know which program is writing into it. It maybe many programs simulatenously, or it may be the kernel asynchronously, etc... If you want to change that you would have to make the architecture tremendously more complicated and less flexible.
And the same goes for shells. You don't want to complicate the architecture just so that a lawyer could attest you that "it was cat" who drew the image und some weird interpretation. Nothing would be gained, and nobody would be able to understand what's happening anymore.