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