Yes, blue is discounted redemption, however it is not a separate cabin, it is the same economy cabin.
And the general rule for lounge access (and the onboard service recieved) is that it does not matter how you are booked into the cabin (full fare, discount fare, full miles, discounted miles), you get everthing that goes with the cabin 'class' of serivce.
You are a economy passenger connecting onto longhaul business. You should get access.