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