Encontre la solucion la dejo por si alguien le sirve, basicamente era solo aumentar el array que esta en la libreria pChart.class
Código PHP:
var $Palette = array("0"=>array("R"=>55,"G"=>32,"B"=>98),
"1"=>array("R"=>82,"G"=>124,"B"=>148),
"2"=>array("R"=>224,"G"=>214,"B"=>46),
"3"=>array("R"=>46,"G"=>151,"B"=>224),
"4"=>array("R"=>176,"G"=>46,"B"=>224),
"5"=>array("R"=>224,"G"=>46,"B"=>117),
"6"=>array("R"=>255,"G"=>160,"B"=>143),
"7"=>array("R"=>155,"G"=>238,"B"=>290),
"8"=>array("R"=>181,"G"=>110,"B"=>168),
"9"=>array("R"=>94,"G"=>48,"B"=>0),
"10"=>array("R"=>201,"G"=>34,"B"=>0),
"11"=>array("R"=>247,"G"=>143,"B"=>1),
"12"=>array("R"=>255,"G"=>238,"B"=>208),
"13"=>array("R"=>90,"G"=>181,"B"=>110),
"14"=>array("R"=>224,"G"=>100,"B"=>46),
y sigues colocando mas si te van a servir mas colores