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