Nice descriptions there, Allicloud

.
I'd think Spike's case of synesthesia is specifically color-sound synesthesia and possibly color-taste synesthesia. There are different kinds of synesthesia out there. I've shown signs of being a mirror-touch synesthete for as long as I can remember :blink:.
In addition to what has been said about Cera, I also believe she's a very mild Aspie

. I see some of my (and other Aspies') characteristics in her. They are:
*Does not take well to change.
*Likes to be alone often, or so it seems.
*Does not like strangers very much. This could be either change and/or being forced to socialize with an unfamiliar person.
*Mood changes unpredictably. It's said an Aspie's Limbic System is impaired, causing them to not be able to tell when their mood shifts until it's already happened.
*Doesn't care too much for physical contact, but if it's from somebody she already knows, she doesn't seem to mind too much.
*Lastly, she seems to at times have difficulty understanding others' emotions and takes things the wrong way. For example, in the TV series episode about the shiny canyon stones, Tria nicely asks what happened to one of her shiny stones and Cera automatically takes it as an accusation against her and gets snarky with Tria.
That's what I've noticed about her, and if she in fact is an Aspie, her case would be very mild, perhaps as mild on the spectrum as possible.