Try comparing the individual components:
if (base.barRectangle.FillColor.r == Color.Green.r &&
base.barRectangle.FillColor.g == Color.Green.g &&
base.barRectangle.FillColor.b == Color.Green.b){
///Do something...
}
Or you could try writing a color comparison function of your own:
bool isEqualSFColors(SFML.Graphics.Color c1, SFML.Graphics.Color c2){
if (c1.r == c2.r &&
c1.g == c2.g &&
c1.b == c2.b){
return true;
}
return false;
}
Note that I did not include alpha into the comparison (yourColor.a is how you would get it).
SFML is also open source, so you are free to add the operator overloading you desire: http://msdn.microsoft.com/en-us/library/aa288467(v=vs.71).aspx
It's also possible that you are using an older version/binary that you found. I haven't used SFML.net, but I'm sure if you grab a newer copy there may already be this feature built-in.