I found an easier way to paint elements like other elements or to discover the name of any dcolour.  Here it is:

CTRL+D

Press CTRL+D while the cursor is touching a particle to temporarily dispaly the dclolour in the hud, until the cursor is moved; in which case, the dcolour value will disappear and not reappear if the cusor is replaced; you'll have to reperform this action in order to display it again.  If the particle is undecoed, this action while give you the dcolour that matches the color of the element which the cursor is occupying.  In ether case, debug mode must be on in order for this action to work.  People have obviously suggested that dcolour be permanently added to the hud in debug mode; the fact that it hasn't been must mean that doing so would make the hud too big and comical to read.