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