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