Not sure this is exactly what you're trying to do, but it might give you some ideas

Code:

int segs = 6;
int steps = 1;
float rotAdjust = radians (360.0/segs/2.0);
float radius = 95.0;
float segWidth = radius/steps;
float interval = TWO_PI/segs;
int SHADE = 0;
int TINT =1;
float angleInDegrees = 42;

// declare global cols array
color[] cols = new color[segs];


void setup() {  
size(256,256);    
ellipseMode(CENTER);

// populate the array
// could perhaps create a larger more varied colour array, perhaps by using nested loops
for (int i=0; i< segs; i++) {
 cols[i] = color(255-(255/segs)*i, 255-(255/segs)*i,(255/segs)*i);
}

}
void draw() {  
background(128);

pushMatrix();

//start drawing from mouse position  
translate(mouseX, mouseY);
rotate(angleInDegrees);
createWheel(width/2, SHADE);
// back where it should be
popMatrix ();

// keep this small or rotation is too fast!
angleInDegrees += 0.1;

}
// changed parameters
void createWheel (int diameter, int valueshift) {
 if (valueshift == SHADE){
     for (int i=0; i< segs; i++){
       fill(cols[i]);
       arc(0, 0, diameter, diameter, interval*i+rotAdjust, interval*(i+1)+rotAdjust);
     }
     
   }  
} 

You left the rotate() call out of the last version you posted - that will be why it didn't rotate

As for the colour palette: that was just one example of how you might do it.  You could forget all about using 'i' to influence the colour and go for something completely random instead:

Code:

for (int i=0; i< segs; i++) {
 cols[i] = color(random(255), random(255),random(255));
} 

Or even declare several variables in your for loop:

Code:

for (int i=0, j=255; i< segs; i++, j -= (255/segs)) {
  cols[i] = color(255-j,abs(150-j), j);
} 

The important point is that you use 'i' in this case primarily as an index to populate a particular point in the array, rather than creating an array at each iteration