Maybe you could change the blend mode (third parameter) to something like SOFT_LIGHT and play with the color in the second parameter, try to lower it (color(200)).

If you want to...

highlight (slightly brighten) a color

...then I think it is much easier to do it manually. More importantly, this will give you more control to tweak it exactly how you want it. Check out the code example below.

1. color cLow;
2. color cHigh;
3. 
   
4. void setup() {
5.   size(800,800);
6.   noStroke();
7.   cLow = color(100, 150, 200);
8.   cHigh = brightenColor(cLow,50); // increase the brightness of the input color by 50
   
9.   noLoop();
10. }
11. 
    
12. void draw() {
13.   fill(cLow);
14.   rect(0,0,width/2,height);
15.   fill(cHigh);
16.   rect(width/2,0,width/2,height);
17. }
18. 
    
19. color brightenColor(color myColor, int bIncrease) {
20.   float h = hue(myColor);
21.   float s = saturation(myColor);
22.   float b = brightness(myColor);
23.   colorMode(HSB,255);
24.   myColor = color(h,s,b + bIncrease);
25.   return myColor;
26. }