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