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