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