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