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