If dogs cant see colours, then why is my Boxer obsessed with orange?

My Boxer dog has always been obsessed with anything orange. It started when he pinched babies Tigger from Winnie the pooh. He is drawn to anything stripy and orange. He will go straight to orange toys in the pet shop, stuffed toys in charity shop windows and even his favorite blanket he chooses is orange. I find this confusing as i am always told dogs cant see colours. Is this true?