How to fill correct answer in short question use Match against a regular expression??

I dont know how to use correct answer in short question when i choose
Match against a regular expression (answer must match the supplied regular expression)
i get the error when i use this regex:
(|they('| a)re )colou?rs
can any one give a simple example please !
i copy from this link https://docs.moodle.org/38/en/Regular_Expression_Short-Answer_question_type

because no example in the module at all

thanks