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