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