Before this fix, the field 'color' was hardcoded in the m2m_tags widget, which means that: - one couldn't specify another field (problem for custom models, with x_...) - if the related model didn't have the field 'color', a warning was raised by the server Now, the color attribute needs to be specified on the widget options if one wants to display colored tags. If the color is not specified, the tags will be displayed in grey.