the simplest solution would be to just add a constant for the light color in the pixelshader:

Code:

---

PixelShader= 

asm

{

  ps.1.3

  def c0,0.3,0.3,0.9,1.0 // light color rgba

  tex t0 // sample colormap

  tex t1 // sample normalmap

  dp3 r1,t1_bx2,v0_bx2 // normal . light

  mul r1,r1,c0 // modulate light intensity against light color

  mul r0,t0,r1 // modulate light against color(t0)

};

---

(i haven't tested it! instead of mul r1,r1,c0 you could also try mul_x2 r1,r1,c0 or something like that...)

if you want to pass the color from outside of the shader it gets a little more complicated. i guess then you would have to pass it first to the vertex shader and from there to the pixelshader...