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