How far away from each other should I plant my Hydrangea plants?

I have about 10 feet of space to work with.I'm trying to figure how many plants to get. And how do I get them blue/purple?

How far away from each other should I plant my Hydrangea plants?
Hydrangea: Mopheads, with large ball like blooms. The lacecaps are quite different - each flat flower-head has an outer ring of large flowers surrounding a central group of much smaller ones. Blue flowers only appear under acid conditions - in order to 'blue' Hydrangeas in alkaline soils it is necessary to apply blueing powder (which can be obtained from any good garden centres) every 7-14 days. Hydrangea bushes grow approx. 5 ft x 5 ft. Good soil, plenty of water, protect in winter from against heavy frosts.
Reply:You have to buy them either blue, pink, or white; plant 4 ft. apart; plant azaleas or impatiens between.
Reply:4-6 feet is the proper spacing for hydrangeas. Crowding them may result in disease and a lack of blooms.