Simple coffee grounds in the soil will make them blue. Don't know about the brown spots. Just dump your coffee grounds out onto them and you'll see the results very quickly...
Will Fertilizer For Azaleia's Turn My Hydrangea's Blue? And Also They Have Brown Patches On The Leaves. What Is The Cause And What Do I Do ?
This is what I do with my hydrangeas. I use miracid (in the pink box) from miracle grow on the leaves and soil. Dump the solution of the leaves also because the leaves will soak up the solution also. If you want to put a steel nail in the soil you can also. You will find some of your flowers blue (from the miracid) and pink (from the steel nail).