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)(11,16)(12,14)(13,15)(17,18,21,19)(20,23,24,22)(25,26)(27,28)(29,37)(30,31)(32,36)(33,39)(34,38)(35,40)(1,3,5,6)(2,4,7,8)(9,11,13,12)(10,14,15,16)(26,31)(27,32)(33,37)(34,40)(9,11,13,12)(10,14,15,16)(17,19,21,18)(20,23,24,22)(25,27,30,32)(26,28,31,36)(29,34,39,40)(33,35,37,38)(1,2)(3,4)(5,7)(6,8)(9,12,13,11)(10,14,15,16)(17,20)(18,22)(19,23)(21,24)(25,28)(26,32)(27,31)(29,38)(30,36)(33,34)(35,39)(37,40)(1,4)(2,6)(3,7)(5,8)(9,10)(11,14)(12,16)(13,15)(25,29,30,39)(26,33,31,37)(27,34,32,40)(28,35,36,38)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.