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