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