adobe photoshop - How to create an image with complex gradient?

I need to create an image like this, but I do not know what software or technique to use. I tried to use the Mesh Tool in Illustrator, but the result is odd, also I tried to blur an image in Photoshop, but I need to use some particular colors.

Answer

Using Photoshop

• Over a colored background, use the Lasso Tool to create an irregular selection



• With this selection make a Color Fill Layer with the dark color


• Click on the Mask Thumbnail


• Menu Filter > Blur > Gaussian Blur

Result