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