I, and a lot of others in Toronto, have Dwarf Alberta Spruce trees which have browned on one side. I suspect this may be due to the unusual winter. What can be done to return them to green?
It is very likely winter damage indeed. Dwarf Alberta Spruce are susceptible to harsh weather and this has been one of the harshest winters in a very long time.
However, be patient, your tree may not be lost. Wait until new growth appears and see if you can gently clip away the brown damaged tips, leaving the new growth to disguise where the damage occurred.
The University of Minnesota (where they always have rough winters) has a very good explanation of the damage, repair and how to prevent future damage. You can visit their website at https://www.extension.umn.edu/garden/yard-garden/trees-shrubs/protecting-from-winter-damage/
Here’s hoping your little spruce will be looking better by the fall!