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