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