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