How about an orgasm rev meter starting in blue progressing to green, yellow and then red?
I reckon Hot Wheels would want that accessory mounted on his bed dash.
About the dream: I suspect it might relate to something quite banal such as his wife having a PAP smear but which when considered from the male's twisted point of view (only the male, ok) seems erotic as the vagina is held wide open by a speculum and brush or cervical scraper held by the doctor/nurse (stranger) collects cervical cells which are then transferred onto a slide and sometimes a vial of preservation fluid.........which yep turns brownish red!
There it all fits nicely but then I'm a bit of a bs artist

Oops, not quite; there was little chance of orgasm!