plotting - Plot 4D data with color as 4th dimension

I have a list of 4D data (x position, y position, amplitude, wavelength). I want to plot x, y, and amplitude on a 3D plot and have the color of the points correspond to the wavelength. I have seen many examples using functions to define color but my wavelength cannot be expressed by an analytic function. Is there a simple way to do this?

Answer

Here a another possible way to visualize 4D data:

data = Flatten[Table[{x, y, x^2 + y^2, Sin[x - y]}, 
    {x, -Pi, Pi,Pi/10}, {y,-Pi,Pi, Pi/10}], 1];

You can use the function Point along with VertexColors. Now the points are places using the first three elements and the color is determined by the fourth. In this case I used Hue, but you can use whatever you prefer.

Graphics3D[
   Point[data[[All, 1 ;; 3]], VertexColors -> Hue /@ data[[All, 4]]],
   Axes -> True, BoxRatios -> {1, 1, 1/GoldenRatio}]