Does anyone know how to correct for reddening in a CC-diagram?

[tyskstil]

Main Question or Discussion Point

I have an observed spectrum for an object (magnitudes at 4 wavelengths) and need to correct for reddening before placing the object in a CC diagram... I have some color excess ratios, but I am not sure how to use them...

 

[tyskstil]

Specifically:

My spectrum measured by Spitzer at wavelengths:
lambda (mu m): 3.6, 4.5 ,5.8 and 8.0
magnitude (mag): 12.954, 13.015, 13.091, 12.917

The color excess ratios defined through E(Ks −[lambda])/E(J−H) at each lambda are:
0.39, 0.47, 0.56, 0.555

I am not sure how to use this.