import re
colors=['red','gray','black','white','brown']
animals=['fox','bear','hare','squirrel','wolf']
pattern = fr"(?i)\b(?:{'|'.join(colors)})\s+(?:{'|'.join(animals)})\b"
doc_string = "Hello, red fox! Hello Black Hare! What's up whItE sQuirrel, brown wolf and gray bear!"
print ( re.findall(pattern, doc_string) )