One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,4,8,5,6,3,7)(9,10)(11,20)(12,24,28,38)(13,29)(14,18)(15,19)(16,22)(17,27,35,26)(21,31,25,34)(23,32)(30,33)(36,37,40,39)(2,6)(3,4)(9,11)(10,16)(12,25)(13,30)(14,22)(15,23)(17,34)(18,32)(19,33)(20,29)(21,28)(24,36)(26,37)(27,39)(31,35)(38,40) involution — undirected(2,7,6,8)(9,12,13,26,15,28,14,27)(10,17,18,24,19,35,29,38)(11,21,22,37,23,25,30,39)(16,31,20,36,33,34,32,40)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.