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