Rebecca, thanks for asking for comments about the Zebra Finch you saw in El Paso Co and reported to eBird.

[Joe Roller]

I looked up Zebra Finch on the eBird Species map.

Native to Australia. 

NO eBird reports for USA, other than one soft report (heard only) from Florida, escaped cage bird.

So I conclude that either eBirders dont submit Zebra Finches or if they do,

eBird does not accept them.

Next, I looked up "cage birds" on. at eBird HELP section.

Nothing there.

Found this on eBird:

What birds should NOT be reported on my checklist?

eBird is intended for observations of wild, living birds. Please do not report dead or captive birds (e.g., do not include birds in a zoo exhibit or pheasants on a farm). 

You MAY report any unrestrained bird you observe in the wild. However, please indicate suspected domestic or escaped birds whenever possible. Note that domestic, exotic, and escaped birds may be marked "Rare" and/or unconfirmed by our reviewers so these birds do not get confused for wild, naturally occurring species in our public database. For more information, see our eBird Rules and Best Practices.

OR in order to save reviewers time, you could submit a checklist for wild birds you saw in that hour near the Zebra Finch,

eg, "Canada goose" and "House Finch" and mention the Zebra Finch in the comment section.

Then you'd have a personal record of it, but not gunk up the eBird system with a bird 

that is clearly an escapee and not a natural part of Colorado's avifauna.

eBird reviewers' time is precious and it's best not to add even one bit to their loads.

Although you MAY report escapees, you can also choose NOT to do so.

Disclaimer - this is not in knowledge bucket, but tried to find out what I could.

A CO eBird species reviewer will probably chime in with a better answer.

Joe Roller, Denver