Hope you can help me because I googled it and couldnt find the right aswer!
The thing is that I am using Adobe Flash CS5 Professional and for the brush tool I cannot modify the stroke colour or size, or style..the only thing I can change is the fill..
As far as I know, the brush tool does not have a stroke, just a fill, so there should be no adjustment for it. For the others, can you show a screenshot of your tool panel with the brush tool selected? That is where the adjustments are made.
While the image that sudeshna sarkar does not show them, as I already inducated - at the bottom of the tool panel (the panel to the right with the brush tool selected and circled with yellow) is where you will find the brush size and style options.