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