According to the construct classic wiki, a solid object will only prevent other objects that have behaviors such as the "platform" or "8 direction" behaviors on them from passing through each other.
sourceforge.net/apps/mediawiki/construct/index.php
Unless I am missing something, your red and green objects are both marked as solid, however neither of them have the "platform" or "8 direction" behaviors added to them.
I can't post hyperlinks so you will need to copy and paste that link manually.