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