to detect specific proteins -

one may use antibodies to that protein tagged with fluorescent molecules (as rhodamine red, Cy3 = orange, evans blue, fluorescein = green) which will bind to it and fluoresce.

picture is of rat intestine tagged with yellow-green fluorescing antibody for GLUT 2 for glucose transport.

is present in basal & lateral sides of epithelial cells, but not in brush border area.  

rat intestine - GLUT2