How to create an abstract image in photoshop ?

Go on "File" & then "New".

Click on the brush sign. Then, select your brush.

Paint the sheet all black.

Set the background color to white.

Stamp the white brush a few times.

Press "Ctrl" + "J". This will give you a new layer.

Click on "Filter" -> "Blur" -> "Gaussian Blur".

Set it to around 5 pixels.

Pick the brush numbered "300".

Pick a color, paint half of it.

Pick another color, paint the other half.

Look on the right you will see your layer. Right Click (On your layer) -> "Blending Options".

Set it from Normal to Color.

Press "OK".