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