Hmmm... I would say space-space (word - word) would have to be seen as an intended separator by search engines, which is the common usage I've seen in a title, and I'm not sure about : being a separator in strict usage interpretation, or even search engine interpretation.
It's actually usually a character indicating the information following it provides a list, clarification or explanation of the preceding, so it's strictly more of a character indicating a "definition of some type follows". The context of : usually relates to a "concept" or "idea" preceding and "more information", a "definition", or an "explanation" following. (In US English anyway. It's usage and interpretation actually varies from language to language.)