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)(11,15)(12,20)(13,22)(14,18)(16,21)(17,23)(19,24)(25,26)(27,30)(28,31)(29,32)(33,37)(34,36)(35,38)(39,40) involution — undirected(1,3,4,8)(2,5,6,7)(9,11,14,12)(10,15,18,20)(13,19,23,21)(16,22,24,17)(25,27)(26,30)(28,33)(29,34)(31,37)(32,36)(35,39)(38,40)(9,12,14,11)(10,16,18,24)(13,19,23,21)(15,22,20,17)(30,36)(37,40)(2,6)(5,7)(11,12)(15,20)(16,24)(19,21)(25,28,29,35)(26,31,32,38)(27,33,34,39)(30,37,36,40)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.