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