I would like to severely limit my water use.

The plants that actually like this in my yard are: globe thistle; lavender; geranium.

The plants that want more water are: echinacea; delphinium; marigold.

Any other plants with water needs similar to the first list? I would like to grow lots of greenery, as well as yellow/red/purple flowers.

I live in Wyoming - also hot, dry summers and cold, dry winters. Some of the xeric plants that work in my garden are: gaillardia, iris, russian sage, salvia, red hot pokers, coreopsis, snow-in-summer, various ornamental grasses (check out bluestem.ca), catmint, oriental poppies, dwarf sundrops, sedum and yarrow. And there are many more.

I would suggest you google xeriscaping and look for the sites out of colorado - their climate in similar (zone 5) and they have a lot of good info on xeriscaping. Especially look for Colorado State Univ. sites. Also you might want to look at highcountrygardens.com. They specialize in xeric plants and while not all of their stock in cold hardy, much of it is. Happy hunting.

Yucca (many species,evergreen,easy to grow,check hardiness)
Black-eyed Susans (tolerates drought/heat), yellow flowers
Purple cone flower
Russian Olive tree
Ice Plant (check for cold hardy varieties only)
Many herbs: lavender, Rosemary Arps (Arps hardy to zone 6b)
Oregano
Bay (hardy to about zone 7 outside)
Thyme
Hardy Opuntia Cactus
Sempervivum (Hens and Chicks)
Some agave species (check for hardiness)
Ornamental Grasses