There are countless variations on that. I've always been partial to this one:

    Y es que en el mundo traidor
    nada hay verdad ni mentira;
    todo es según el color
    del cristal con que se mira

which roughly translates to: "and it's that in this treacherous world, there is truth nor lie; everything has the color of the glass(es) through which we look", from Ramón de Campoamor, a 19th century Spanish poet.