用setColor给CC3LineNode对象指定颜色时，有时画出的线条会变色，没有变成指定的颜色。
CC3LineNode官方介绍：http://brenwill.com/docs/cocos3d/0.5.4/api/interface_c_c3_line_node.html
其中有一句：
To color the lines, use the pureColor property to draw the lines in a pure, solid color that is not affected by lighting conditions. You can also add a material to your CC3LineNode instance to get more subtle coloring and blending, but this can sometimes appear strange with lines. You can also use CCActionInterval to change the tinting or opacity of the lines, as you would with any mesh node.
说明指定颜色用pureColor就不会出现类似的问题。