The Basque Government placed an order for 723 new polo shirts and 174 pairs of trousers for their Ertzaintza police for back in December 2012.
The official colours of the force are navy blue, black, read and while.
But the new Basque police uniforms came back in a shade of green.
Officers have reacted angrily to the mix-up with many refusing to pick up the new kit, saying it looks "more Civil Guard than Ertzaintza", Spain's El Correo newspaper reported recently.
Spain's national Civil Guard force get around in a distinctive green uniform.
A spokesperson for the Basque Government's Security Department laid the blame for the mistake on administrative staff within the agency.
The green colour had been chosen by those staff as a matter of urgency, the spokesperson.
The uniforms were needed in a hurry for new recruits in the traffic units, and the green fabric was the only one the preferred supplier had available.
When the department discovered it had been landed with a pile of uniforms in the wrong colour, it tried to return them to the supplier.
But the supplier refused, citing contract conditions.
Some Ertzaintza police have now taken the polo shirts and slacks home, while others are refusing to have anything to do with the uniform.