Step 2 : Now let's use the color of the memory chips symbol to designate the two different chip types. To do this , click on the MEMORY model entity and click on "Add Additional Symbol" in the " Additional Symbols " section of the "symbols " tab . You can color one symbol red and the other green by simply selecting one of the " Ative Symbol" and changing its color. Please note that these two symbols are numbered zero and one (not one and two ).