morning dress

Hi everyone. Does anyone happen to know when duck egg blue and other pastel colors became popular as waistcoat colors with morning dress? Have they been around a long time or is it a relatively recent trend?

Hi all, Does anyone have any ideas about this waistcoat? It's backless, so must be post-1923 (though I think it's probably much later than that anyway), it has what looks like would have originally been four buttons for a slip (only one remains) and the buckle reads 'SOLIDE'. Thanks!