A search via RegexPal could look like this:
Search: \\x .*?\\x\*:::( \d+):(\d)
Replace: \1.\2
Where \\x .*?\\x\*
means: search only inside of cross references
The three colons :::
separate between the context search expression and the actual search
Actual search expression: ( \d+):(\d)
One or more digits, followed by a colon and then another digit
Replace: Put together the content of the first expression in parens, a literal dot and the content of the second pair of parens
(I don’t know of any regex online sessions.)