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