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