2003 RM250 What rear spring do I have? Its red.

I bought a used 2003 RM250, the thing still looks new. I was going through the manual to see which rear spring I have. The manual lists four different spring options; green, pink, black and blue. My spring is red.

Does anyone know the rate for that spring? Is there a way to find the spring rate, with out using a scale?

Thanks, Steve.