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