Removing text from Cell that does not fit pattern

I have an Excel file that has additional commentary added to Cells and multiple values that I need to capture also in the same cell. The value of a single cell in the spreadsheet may look something like:

This is my comment number 1

This is my comment number 2

John:Silver

This is. my comment number 3

Andrew:Gold

This is my comment number 4

What I am trying to extract from this cell is:

John:Silver

Andrew:Gold

I have been reading about text to column parsing but that seems to expect the data to be more structured. I am currently experimenting with the RegEx parsing option, but I am not sure it would return the multiple values in the cell. Has anyone done this already?