Your vest can be the same colour as the rest of the power suit to add subtle elegance or stand out using a subtly contrasting colour. For instance, the suit may consist of a pattern weave, which works best with dark and muted colours. A great example would be herringbone, which remains conservative while blending in with colours like charcoal or navy without losing visual interest.
Either way, there must be no gap between the vest and the trousers. The shirt should not be shown tucked into the pants. A great way to maintain the proportion of the outfit is to opt for a higher waist on the trousers.
The fit should be modern and flattering without being overly tight. The overall objective should be towards confidence. Similarly, aim for classic and conservative details such as notched lapels, straight flap pockets, and side vents. Ticket pockets and contrast stitching are indeed possible but won’t be quite as effective.
Furthermore, consider a plain white cotton pocket square in a classic TV fold. This choice of the pocket square would be an excellent detail, whereas other folds and styles may risk being too flamboyant. Similarly, luxury cufflinks that use simple metallic colours are particularly effective.