This is a very colorful painting and is one of my favorites. I did this in poster colors. This is a very simple painting. After drawing the picture, I start with the background. I used a very light green for this. You can also use other light colors like Baby blue, baby pink etc. After painting the background. I started the colors inside the wings which is the rainbow colors. After finishing those colors. Take a darker shade of those colors that are;

For :-

Red: Red + Black = Maroon

Orange: Orange + Red = Saffron

Yellow: Yellow + Orange = Dark yellow

Green: Green + Dark green = Leaf green

Blue: Use dark blue or Prussian blue

Purple: Purple + Black = Dark Violet

With those colors, outline their respective base color. Ex. For Red you have to outline with Maroon. Do the same with other colors too. Then I did the body of the butterfly in gray color. Finally, I did the black part. And thats it! I like this painting because it is simple, beautiful and colorful and the rainbow colors go very well with the black.