how do you create this type of gradient ?

[denzjos]

I tried a quick example. I selected the purple/red and made 2 layers with this selection, the upper layer the selection filled with purple/red and lower layer filled with white and set the original not visible. Then made a blue layer under the white layer. Then moved the white layer a little up and left to create the white border an blurred this layer (value 1). Then I made a few layers with different white round brush dots and blend them in the purple areas (play with the layer opacity). I also  used a purple dot on the upper-left and blend it with a gradient mask. Not perfect, just a try.