list manipulation - How to blend some colors on a curve

I need to define a color gradient on a 3D curve, but I'm having some problems with this.

Suppose we have a 3D curve defined as a parametric function of some real variable phi :

curve[phi_] := {...};

where phi runs from phi1 to phi2. Now, I defined the start, middle and end colors like this :

Color1 := RGBColor[0.99, 0.2, 0.2, 0.2];
Color2 := RGBColor[0.2, 0.99, 0.2, 0.8];
Color3 := RGBColor[0.2, 0.2, 0.99, 0.2];


CurveColor[phi_] = Blend[{Color1, Color2, Color3}, phi];

The last definition doesn't work. I need the function CurveColor[phi] to output four real positive numbers smaller than 1, like this :

CurveColor[phi1] := {0.99, 0.2, 0.2, 0.2}
CurveColor[phi2] := {0.2, 0.2, 0.99, 0.2}

The colors should blend smoothly between Color1 to Color2 to Color3, and be uniformly distributed along the interval phi1 to phi2).

So how should I define that color function ? I don't need that function to be used in a plot3D. I only need the color data as a list of numbers.

Please, notice that I'm working with Mathematica 7.

Answer

Since you only want the numbers, you can get them by using Apply:

CurveColor[phi_] = List@@Blend[{Color1, Color2, Color3}, 
       Rescale[phi, {phimin, phimax}]]

which will ensure that you always use the same blending functionality that Blend uses. Note, the use of Rescale.