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