The question: Is it ever advisable to forgo white trim and mouldings for a contrasting colour? How high-contrast can I go without making the overall effect too wacky?
The answer: Of course there are many approaches to how you dress a wall. The most common is a coloured wall with the white trim around doors and windows plus a white cornice to break the wall from the ceiling. This allows you to add a hint of colour on the ceiling while maintaining the crispness.
White trim contrasted to colour – or even paired with a white wall – is like a classic pressed white shirt: timeless. That said, a coloured shirt with contrasting cuffs and collars might be a little wacky but can look great on occasion.
I love Hermès orange, for instance, trimmed out in a soft silver grey. I prefer trim that isn't too high-contrast, except in a child's room. A great look is keeping the walls and trim the same colour while distinguishing the difference through sheen level – e.g., flat ceiling, eggshell walls and semi-gloss trim.