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