I have a lot of variegated plants growing on my Oasis.
Variegated Vinca also has attractive purple blooms.
Variegated Petasites has large leaves and likes a lot of moisture.
This Forsythia is variegated and very yellow, too.
The Tri-colored European Beech(Fagus) is one of the most attractive trees in spring, though the tips burn some in the Iowa Sun.