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