RegEx capture everything before keyword but after the opening bracket

Test string:

[valign px=-2][center][bgcolor=GREEN]TESTING[/bgcolor][/center][/valign]

I have come up with color.*?\] which almost works... It gets everything after the keyword up to and including the closing bracket:

color=GREEN]  AND  color]   ---> Target ---> [bgcolor=GREEN]  AND  [/bgcolor]

I just can't get how to make the same in reverse

\[.*?color.*?\] this gets me the whole string before the key up to the closing bracket - [valign px=-2][center][bgcolor=GREEN] BUT it also correctly gives me [/bgcolor] without TESTING in between them

I'm using https://regex101.com/ for testing

Solution

If you want to get [bgcolor=GREEN] and [/bgcolor] with leading lowercase characters for color and uppercase chars for color for the value, you might use:

\[\/?[a-z]*color(?:=[A-Z]+)?]

See a regex 101 demo

Or a bit more broader match using a negated character class denoted with [^

\[[^][=]*color(?:=[^][=]+)?]

The regex in parts matches:

\[ Match [
[^][=]* Match 0+ times any character except [ ] or =
color Match literally
(?:=[^][=]+)? Optionally match = and 1+ times any char except [ ] or =
] Match literally

See a regex 101 demo