How to plot a function and each starting value in different colors? (Newton's Method)

I have to plot a dot at each starting point (x0, 0) in red, green and blue, if the method converges to the roots of the function (roots = 1, 2, 3), respectively. If the method fails I have to plot a diamond.

This is my code:

NewtonMethod1D(@(x) x.^3-6*x.^2+11*x-6, @(x) 3*x.^2-12*x+11, 0:0.1:4, 1.e-12, 10)

x = [1 2 3];

colorstr = 'rgb';

if x == 1 x == 2 x == 3

for i = 0:0.1:4

plot(f, f(x))

hold on

plot(i, 0, 'color', colorstr(i))

end

else

for i = 0:0.1:4

plot(f, f(x))

hold on

plot(i, 0, 'kd')

end

end