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