It looks like a Caesalpinia Mexicana to me.

But its hard to tell without seeing fully developed bark.

↑ imo the leaf shape seems off

apparently.
when i google imaged "mimosa hostilis flower" i saw 7 pictures of silk mimosa flowers, and only 3 white ones (which admittedly i didn't even notice, as i gave it such a cursory glance)..

my mistake

EDIT: also are you/they sure it is a mimosa genus, not just a mimosoideae/mimosaceae subfamily or mimosae tribe?
the only yellow flowers i can find in mimosa genus are little puffballs (almost like acacia flowers).

The plant with the pink flower is common around my neighborhood - I will ask my local nurseryman for a correct ID ... BTW , yes , I believe that both species are fabiacaes ...

I have just been to my local nursery , taking with me a cutting of the pink flowered plant , collected on the way ... It is a Calliandra [ according to the proprietor ] , possibly C . Tweedii . . And yes , somebody above suggested the yellow-flowered specimen might be a Caesilpinia , which was my thought also at first , but I do not know enough myself to speculate on that one ...

i know those grow all over california..

it is mimosoideae, but idk if it has been tested for actives or not.