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