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