legend

digraph legend
{
   rankdir=LR;
   node [shape=box, style=filled];
   experimental      [color=crimson,     label="Experimental"]
   proposed_standard [color=orange,      label="Proposed standard"]
   draft_standard    [color=yellow,      label="Draft standard"]
   internet_standard [color=green,       label="Internet standard"]
   standard          [color=green,       label="Standard"]
   informational     [color=deepskyblue, label="Informational"]
   obsolete          [color=red,         label="Obsolete"]
   unknown           [color=gray,        label="Unknown"]
   old1              [color=red,         label="Old"]
   new1              [color=gray,        label="New"]
   old2              [color=green,       label="Old"]
   new2              [color=deepskyblue, label="New"]

   old1 -> new1 [label="Obsolete", color=red]
   old2 -> new2 [label="Update",   color=blue]
}