Can't print values when colors is set in Style object

[luigonsec]

I am trying customize a Bar chart using pygal and I am getting troubles with custom style. I want set a color for each serie, so I add the colors parameter in a Style object creation:

custom_style = Style( colors = ( 'red' , 'blue' ) } )

I add a couple options
config.style = custom_style
config.show_y_guides = True
config.show_legend = True
config.print_values = True
config.print_values_position = 'top'

And the values are not printed. However, If I create a default Style object

custom_style = Style()

And after I add the others options, the chart is correctly rendered and the values are printed.

What is happening?

[paradoxxxzero]

Do you have a full example?