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