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