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