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