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