One vertex per element, one color per generator, with an edge from x to x·s.
(1,2) involution — undirected(3,4,6,5)(7,8,13,18,14,19,12,17)(9,20,24,15,25,32,23,33)(10,26,27,35,28,34,11,16)(21,37,29,36,22,30,38,31)(3,5,6,4)(7,9,14,25)(8,15,19,33)(10,21,28,22)(11,29,27,38)(12,24,13,23)(16,30,35,37)(17,32,18,20)(26,36,34,31)(7,10,12,11,14,28,13,27)(8,16,18,26,19,35,17,34)(9,21,24,29,25,22,23,38)(15,30,20,36,33,37,32,31)(7,11,12,28,14,27,13,10)(8,16,17,34,19,35,18,26)(9,22,23,29,25,21,24,38)(15,31,20,30,33,36,32,37)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.