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)(11,20)(12,25)(13,15)(14,19)(16,24)(17,27)(18,26)(21,29)(22,36)(23,32)(28,30)(31,35)(33,40)(34,37)(38,39)(2,5)(6,8)(10,15,19,18)(11,21,24,23)(17,30,33,25)(22,35,38,37)(1,2)(3,5)(4,8)(6,7)(9,11)(10,16)(12,22)(13,23)(14,24)(15,29)(17,31)(18,32)(19,20)(21,26)(25,39)(27,37)(28,38)(30,36)(33,34)(35,40) involution — undirected(9,12,26,40,14,28,13,27)(10,17,15,30,19,33,18,25)(11,22,21,35,24,38,23,37)(16,31,29,36,20,34,32,39)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.