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