RegEx - Match Numbers of Variable Length

What regex engine are you using? Most of them will support the following expression:

\{\d+:\d+\}

The \d is actually shorthand for [0-9], but the important part is the addition of + which means "one or more".

{[0-9]+:[0-9]+}

try adding plus(es)

Try this:

{[0-9]{1,3}:[0-9]{1,3}}

The {1,3} means "match between 1 and 3 of the preceding characters".