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