SoQuadMesh + color node interpolation

I have a collection of points (nodes) that define a 2d quad mesh. The third dimension is a scalar function. From this 3rd value of every node I define a color. So I want to draw a 2d mesh with different colors in the area. Has anyone any knowlegde in coin3d or open inventor and help me with this?

My Code:

SbVec3f *verts;
SbColor *colors;

SoSeparator *signalMesh = new SoSeparator;

pointV = pointList->at(i);

x = pointV->getPoint()[0];
y = pointV->getPoint()[1];
signalLevel = pointV->getSignalLevel();

verts[i].setValue(x, y, z);

nSignalLevel = normSigLevel(signalLevel,rangeMin,rangeMax);
//Get the RGB color for this signal level

colors[i].setValue(cr, cg, cb);

// Define material for signalMesh
SoMaterial *myMaterial = new SoMaterial;
myMaterial->diffuseColor.setValues(0,pointList->count(), colors);

// Define coordinates for vertices
SoCoordinate3 *myCoords = new SoCoordinate3;
myCoords->point.setValues(0, pointList->count(), verts);

SoQuadMesh * mesh = new SoQuadMesh;
mesh->verticesPerRow = xpoints;
mesh->verticesPerColumn = ypoints;