Separating colour values from Image in Grasshopper

Hi All,
I’ve been trying to visualise data similar to the "Population Example’’ I have attached, but I don’t know how to extrude the points with specific colours. I understand that I would need identify these colour values and list them into separate lists, but can’t find a solution. I have attached the Rhino and Grasshopper files below (1.2 MB)
Grasshopper Test.3dm (336.3 KB)