Re: how do i remove the blue colour from copper sulphate solution

Richard!  Great question!
   The color of any compound depends on the configuation of the 
electrons.  In this case, it's the copper(II) cation that causes the blue 
color.  The easiest way to change copper(II)'s electron configuration 
(and, therefore, it's color) is with an oxidation/reduction.
   Tables of activity series can show you metals or compounds with the 
strength to reduce Cu(II) to Cu.  Here's a great web page that explains 
the redox process in more detail and has an activity series.  You can tell 
from this table why the iron filings worked.
 http://antoine.frostburg.edu/chem/senese/101/redox/faq/print-activity-
series.shtml

There are other longer, more comprehensive activity series.  Check your 
school's chemistry text book or, if you're brave, the CRC Handbook of 
Physics and Chemistry in the reference section of the library.  Different 
tables are set up different ways, so make sure you know which end is the 
best reducer and which is the best oxidizer.
Here's another site that specifically discusses the color of copper 
sulfate solutions.
 http://antoine.frostburg.edu/chem/senese/101/inorganic/faq/print-blue-vitriol.shtml

I hope this helps.  Thanks for writing in!