Colorful waistcoats with morning dress

I'm sorry I don't have sufficient specific knowledge to answer your question in detail, but I recall elaborate, fancy waistcoats originally having been one of the hallmarks of formal dress, and as time passed what was once dress of a lesser degree of formality succeeded to the role of higher levels, so I would expect that at different periods, colorful waistcoats have gone in and out of vogue with specific degrees of formality.