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