The Catalog of Lightroom CC cannot be opened with Lightroom 5.
You are following the Correct Approach.
However with Creative Cloud you can use Lightroom 5 and Lightroom CC together.See How to Find and Install Previous Version of Adobe Apps in CC 2015 | Adobe Customer Care Team
I also have LR 5.7.1 on my machine but haven't used it since CC came out. now what?
For future Projects you can create a new catalog in Lightroom 5 on your Computer and share the same with your colleague
Else ask your collogue to upgrade to Lightroom CC/6