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