Hi,
  I want to send the output messages in colors.
If a test passed,send the message "Test Passed "to a .txt file in green.
If fails,send the message to the same file in red.
The .txt file is in the same directory where the testcases are located.
Is it possible?
I dont want to use any GUI's...

A .txt file is usually just bare text - a stream of (usually) printable characters - and there's no standard way of marking it up into red or green.   If you were writing .html instead, then you could very easily add appropriate tags.

Now -- if you use a command such as type or cat to display a text file, non-printable characters will be translated according to the screen driver that's in use. So you may be able to use sequences such as those listed here

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