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