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