That's a horrifyingly messy map. However, I am now desperate to book my tickets to the bit of Estella where the Carlists topped the poll.
Green areas are those where Basque is the main language of everyday communication and are thus officially bilingual. Yellow ones are those where Spanish is the primary language of everyday communication but there is significant Basque-speakign minority and/or it underwent the linguistic shift from Basque to Spanish in the 20th century. In grey, monolingually Spanish-speaking regions where either Basque has never been spoken (Tudela) or underwent the linguistic shift to Spanish before the 19th/20th centuries.