Hi Bryan,
The colon is a reserved character in Solr (which the search engine uses). But you should be able to escape it by simply surrounding it with quotes.
So, if you search "My Title: my latest paper" (with the quotes!) that should work to search by the colon. However, if you don't include the quotes, then a field-based search will try to run. For more information on using search in DSpace 7, see the docs at
https://wiki.lyrasis.org/display/DSDOC7x/Search+-+Advanced
Tim