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