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