I am looking for a dwarf tree for container planting. I’d like either a blue hue, but yellow or green is ok. live in zone8

Question

the container I have is about 20″ tall and 20″ across.

Answer 1

The classic "blue hue" tree is dwarf Colorado blue spruce:

See "woody plants" in this article:

https://blog.gardeningknowhow.com/top-of-the-crop/top-10-plants-containers/

This olive is blue hue, but not a dwarf. Although being in a container the growth will be somewhat suppressed:

https://blog.gardeningknowhow.com/trends/growing-arbequina-olive-trees-in-containers/

Here's another article that may help:

https://www.gardeningknowhow.com/special/containers/how-to-grow-container-trees.htm