Planting among our Pahoehoe Lava

We are finally getting around to landscaping our street side yard.  When we prepped the site for the house build (2008) we left as much of the pahoehoe lava in place as possible.  Now it is time to find some salt tolerant ground cover to plant in and between the lava rock croppings.  Zebrina pendula, seen left, is a zone 2 salt tolerant ground cover growing to about 6 inches in height. I like the purple and silver colors.

I would like to pair it with something that is slightly taller and of a different color. I think a "lime" green color would pair well.  I am on the search!

If you have any suggests please comment and I will give it serious consideration.  Remember, I live ocean front in Hawaii so salt is an issue.  Mahalo

Note:  The University of Hawaii, College of Tropical and Humane Resources, has a great white paper on Wind and Salt Tolerant Plants.