Merging colors... How do it with Gimp?

[cli345]

Hi Krikor,

I assume that each circle is on its own layer (with alpha channel).

I suggest this:

• Make all layers invisible (except the involved 3 ones)
  
• Filters -> G'MIC-Qt -> Various -> Custom Code [Full]
  
• Choose "All visible" in "Input layers"
  
• Copy and paste this (in "Code"):
  

Code:

split_opacity
rgb2hsv[0,2,4]
repeat $! l[$<]
    split. c
done done
fill[0,4,8] if(i<60,i*2,if(i<120,i+60,if(i<240,i/2+120,i)))
a[8,9,10] c a[4,5,6] c a[0,1,2] c
hsv2rgb[0,2,4]
100%,100%,1,3
fill. i#0+i#2+i#4
rgb2hsv.
split. c
fill... if(i<120,i/2,if(i<180,i-60,if(i<240,i*2-240,i)))
a[-3,-2,-1] c
hsv2rgb.
100%,100%,1,1
fill. max(i#1,i#3,i#5)
a[-2,-1] c
a[4,5] c a[2,3] c a[0,1] c
mv. 0

• Click 'OK'
  

Hope this helps!