One vertex per element, one color per generator, with an edge from x to x·s.
(1,2) involution — undirected(3,4,6,5)(7,8)(9,18)(10,15)(11,16)(12,26)(13,17)(14,21)(19,32)(20,33)(22,28)(23,29)(24,31)(25,30)(27,35)(34,38)(36,37)(7,9,12,22,13,21,11,20)(8,14,16,28,17,18,26,33)(10,19,23,34,24,35,25,36)(15,27,30,38,31,32,29,37)(3,5,6,4)(7,10,13,24)(8,15,17,31)(9,19,21,35)(11,25,12,23)(14,27,18,32)(16,30,26,29)(20,36,22,34)(28,38,33,37)(7,11,13,12)(8,16,17,26)(9,20,21,22)(10,23,24,25)(14,28,18,33)(15,29,31,30)(19,34,35,36)(27,37,32,38)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.