This is because Tableau does not allow you to apply a color gradient to a specific column - it must be applied to the entire table. You may still be able to find a workaround that meets your needs though - see link below for example.
I did manage to solve the problem to some extent with below Video.
Now i've one more thing to solve for the same above problem. I have more than 2 dimensions for above 2 or more measures.
so KPIs for more than 2 (units) dimensions for more than 2 measures.