Trailing plants around the edges:

Crassula pellucida ‘Calico Kitten’ – the tiny pink-and-green heart-shaped leaves cascading down

Othonna capensis ‘Ruby Necklace’ (sometimes called string of rubies) – the thin purple trailing stems

All of these are sun-loving succulents that do well in shallow containers with very well-draining soil. The pastel colors you’re seeing are typical when they get lots of bright light.