Not publishing some code here is like barking the wrong tree! 

Colors in the pixels[] array are always stored in RGB, whatever the current color mode.

@PhiLho, thanks for the response, and that was my understanding.

Below is a simplified version of the draw part of the code. A multilevel approach is set up, the level number of which can be adjusted on the fly. Each xy location is scanned and processed for each level pass. In earlier version of the program, the desired results were obtained by stacking transparent points equal to the level number on top of each xy location, and that legacy code is retained in one of the two evaluation approaches seen below.

The newer approach is to do the same thing, except to evaluate a pixel instead of a point on each pass, and sum the accumulated pixel values. Happily, the visual results are almost identical, with some increasing variance depending on user settings.

This all needs to be done in HSB color mode. I don't know if lookup tables or bitwise operations or anything else would really help, as those are things I simply haven't mastered yet, hence the request for guidance.

1. void draw() {
2.  
3.   colorLevel = 100;
4.   colorLevel += incColorLevel;
5.   noiseSeed(noiseSeedVal);
6.  
7.   if (toggleFlow) z+= 0.7;      // Animation.
   
8.   for (int level = 0; level < levelNum; level++) {  // Multiscale loop.
9.     colorLevel = (colorLevel - (colorLevel/levelNum));  // Scale color levels.
10.     noiseDetail(int(colorLevel * .1), colorLevel / 100);  // Scale noise detail.
11.     for (int y = 0; y < height; y++) {
12.       for (int x = 0; x < width; x++) {
13.         colorVal1 = (noise((perlin * x) * incX + panX, (perlin * y) * incY + panY, (perlin * z)) * colorLevel) % mod;
14.        
15.         // [Trig and other Math Functions for UI go here.]
    
16.        
    
17.         // Multiscale Color Evaluation.
18.         if (toggleEvalMethod) {
19.          
20.         // Pixel Evaluation.
21.         if (toggleGray) {
22.         currentColor = color((colorVal1 / colorLevel) + shiftHue, colorLevel + shiftAlpha);       
23.         }
24.        
25.         else {
26.         currentColor = color((colorVal1 / colorLevel) + shiftHue,
27.         (colorLevel * levelNum) + shiftSaturation,
28.         colorVal1 + shiftBrightness,
29.         colorLevel + shiftAlpha);
30.        
31.         }
32.      
33.         if (level > 0) {
34. //          lastColor = get(x, y);
35.           lastColor = pixels[y * width + x];
36.           cumulativeColor = blendColor(lastColor, currentColor, BLEND);
37. //          set(x, y, cumulativeColor);      
38.           pixels[y * width + x] = cumulativeColor;
39.         }
40. //        else { set(x, y, currentColor); }
41.         else {  pixels[y * width + x] = cumulativeColor; }
42.         }
43.        
44.         else {
45.        
46.         // Point Evaluation.
47.         if (toggleGray) {
48.         stroke((colorVal1 / colorLevel) + shiftHue, colorLevel + shiftAlpha);
49.         }
50.        
51.         else {
52.         stroke((colorVal1 / colorLevel) + shiftHue,
53.         (colorLevel * levelNum) + shiftSaturation,
54.         colorVal1 + shiftBrightness,
55.         colorLevel + shiftAlpha);
56.         }
57.        
58.         point(x, y);
59.   
60.         }    
61.        
62.       }  // End X.
63.     }  // End Y.
64.   }  // End Multiscale.
65.       println(frameRate);    
66.      updatePixels();
67. }  // End Draw.