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