This is my favorite recipe for homemade glass cleaner. It works great! If you want it blue just add a drop of food coloring but really there is no need to do so.
1 cup alcohol
1 cup water
1 tbsp white vinegar.
Mix all together and store in a spray bottle. Please do not forget to label the bottle so everyone knows what it is.
This mixture could also be used on sinks, countertops, etc....