Assuming the correlation is of a linear type, then you could use a method known as linear regression/method of least squares, to map an equation of the form y=mx + c for each dataset.
That is to say have a linear equation for the red, blue and green data points.
Once equations have been derived for each dataset you can intelligently obtain some sort of pattern (correlation) between them.
If the data is not of a linear type, then things become more complex, although the method of least squares can still be applied. For instance, suppose that the equation is quadratic, meaning that f(x) = ax^2 + bx + c, where a, b and c are not yet known. We now seek the values of a, b and c that minimize the sum of the squares of the residuals:
[tex]S=\sum_{i=1}^n(y_i-f(x_i))^2[/tex]
Simple as pie.