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