Good afternoon, all. Thanks for the question, Kay. It’s good to see you active in the forums as well.
Colle isn’t truly, in itself, a type of bow stroke. In English, “colle” translated to “glue.” It refers to the idea of keeping control of the beginning and end of all bow strokes by focusing in on the fingers on your bow hand – especially in highly-articulated strokes such as martele and slurred staccato.