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)(11,18)(12,16)(13,15)(14,21)(17,22)(19,23)(20,24)(25,26,31,28)(27,35,36,32)(29,33,40,38)(30,39,37,34)(1,2)(3,5)(4,6)(7,8)(9,11,15,12)(10,16,13,18)(14,19,22,20)(17,23,21,24)(25,27)(26,32)(28,35)(29,30)(31,36)(33,34)(37,40)(38,39)(10,13)(11,12)(17,21)(19,20)(27,36)(29,40)(32,35)(33,38) involution — undirected(1,3,4,7)(2,5,6,8)(9,12,15,11)(10,16,13,18)(14,20,22,19)(17,23,21,24)(25,28,31,26)(27,35,36,32)(29,38,40,33)(30,39,37,34)(9,13,15,10)(11,16,12,18)(14,21,22,17)(19,23,20,24)(25,29)(26,33)(27,37)(28,38)(30,36)(31,40)(32,39)(34,35)(9,14,15,22)(10,17,13,21)(11,19,12,20)(16,23,18,24)(25,30,31,37)(26,34,28,39)(27,29,36,40)(32,33,35,38)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.