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