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