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