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