What you have to do now is to duplicate the “Rainbow” layer and increase its intensity. Press Ctrl+J to duplicate the layer. After doing so, you will notice that the rainbow is too intense and you may want to reduce it. Lower the value of the Opacity setting, which you will find in the top right of the Layers palette. Lower the opacity of the duplicate layer to about 60-70%.

Now duplicate your “Rainbow” one more time and move it to the right if you want to create a “double rainbow” effect in your picture. Duplicate the layer by proceeding just like in the above step, by pressing the Ctrl+J combination. Now you will have three “Rainbow” layers in the layers palette.

Now move your new copy of the “Rainbow” layer to create a double rainbow.Select the “Move” tool which you will find in the Tools palette (or use its shortcut, by pressing the M key). Click anywhere inside the window and drag the copy of the “Rainbow” layer to the left or to the right of the main rainbow to create a second one. In order to be sure you drag the layer perfectly horizontally, hold the Shift key during dragging.

Usually, when you see a double rainbow in nature you will see that the second one is not as intense as the first one. To make the second rainbow look more natural, you must apply some blur. Press Ctrl+F to re-apply the Gaussian Blur filter with the same settings as the previous time you had used it. To lower its intensity even further, you may find it necessary to apply it one more time (by pressing again Ctrl+F).

If you consider it necessary in order to make some further adjustments to the second rainbow, you can also change its opacity value (you will find this option in the top right of the Layers palette).