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