Which pattern (regex) should I use for splitting a litte text using ':' character as separator?

I need to split a text onto two strings using RegEx (I can not use anyother method).

I have a text like:

This text should be first string: This text should be second string

I need to split the above text onto two string by character ':'. Trying achieve that I have use next pattern [^']: but this is not working. I have tryed another patterns but nothing works.

Any idea which pattern should be the appropiate?

Thank you.