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