The "spectrum" has meaning for people on the spectrum who are aware that they are on the spectrum.
For NT's and people on the spectrum who are not yet aware that they are on any "spectrum" ( ie dont go to websites and dont know about the autism spectrum concept) the word has no meaning.
Rainbows - to me it evokes Jessie Jackson's "Rainbow coalition"- an alliance between races. But it can be differing sexual orientations, or differing neurological types (aspes, adhd types, and neurotypicals), or any group of varying "colors"or flavors or types. So the good news is that "rainbows" can mean anything, the bad news is that rainbows can mean anything. So its too vague for an autism show.
So loose the "spectrum" and "rainbow" ideas.