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