How to assign colors to indicators

Here is an example to change the color of the price bar.  However, it can be adapted to volume, etc.

x:=mov(c,21,s);

up:=if(x>ref(x,-1),x,0);

dn:= if(x<ref(x,-1),x,0); 

flat:= if(x=ref(x,-1),x,0);

up {color me green};

dn {color me red};

flat {color me black};