Spruce trees only keep seven years of needles. All spruce trees not just blue spruce trees. There are no latent buds under the bark of the stems of a spruce tree or spruce shrub. So you cannot prune back into the brown zone where there are no needles. You will never get brand new growth from the interior of a spruce. We are at the end of the summer dormant period for evergreens. In Chicago the first week of August is the last time to do any pruning before the plant needs to be left alone to prep