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