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