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