Unless they are going to be in different viewing sections of the landscape, consider the bloom period of the palo verde, and your flower season and bloom color of the new tree. Bright pink and bright yellow are bold colors, and not automatically a pleasing combo visually. Bright red provides a high contrast to bright yellow, but then the other colors in the garden should to be considered to a greater extent.

They have some nice trees here, maybe you would like to visit and look around for ideas.

http://sdbgarden.org

Another choice on the smaller side might be one of the taller Fremontodendrons. It would have the same water needs and the orangey-gold might be nice with the clear yellow Palo Verde.

Silk Floss tree,Jacaranda's. Brachychiton flame tree. None evergreen though. Most tree's that cover themselves with spectacular colors are not evergreen. On the other hand,some great foliage tree's just have small dull flowers. Nature.

With a Palo Verde, I would consider another themed native in the same endemic area to give your space a related harmony like Prosopis glandulosa torreyana, Prosopis pubescens, Chilopsis, x Catalpa, some accompanying flowering cactus like Saguaro, Echinopsis (flying saucer), Trichocereus, red Barrels, Cereus, Opuntia, Bergerocactus, Cholla, Yucca, Dudleya, Agave, native grasses - desert mallow has nice coral flowers. Also, consider that they all should have similar watering requirements and inorganic mulch, like locally sourced permeable landscape rock and/or decomposed granite.