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