These are managed by removing the new growth right back to the older, brown wood. By doing this you are able to maintain the desired size of the tree and ensure that each year you will have these beautiful, bright colored stems through winter.
Another detail that could be missed just walking by is the woven branches. Most Salix sp. have very pliable new growth, which make them great candidates for bending and weaving and for creative uses in the garden. We saved all the pruned stems and will use them in some display capacity.