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