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