Different coloured pale blue bricks in Tudor corner

I'm building the Tudor corner (set 10350) and the current step I'm on (bag 11), I've noticed that some of the bricks are a more yellow colour than others, specifically the 3x1 pale blue bricks and some of the 2x1 pale blue with side studs. I bought this set completely new, and have only opened the bag with these pieces in today, so they've had no sun exposure since the bags were sealed in factory. Is this intentional, are they slightly different colours, or has there been an error when...