There is nothing like the limey-yellow of some plants to add light to the garden. This golden barberry is one of my favorite to add that bright pop in late summer or early spring. SOme plants start the growing season this way and mellow out to a medium green, while others retain this neon glow.
Here my best list for my zone 4 garden:
Aralia 'Sun King'
Hosta 'Gold Standard'
Japanese False Cypress 'Sagu Suki'
Japanese False Cypress 'Gold Mops'
Lysimachia 'Gold Coin'
Gold Hakone grass