I’ve been meaning to make a tutorial for this ehehe I hope this helps <3

1. let’s take a random manga panel (they’re so fwickin cute)

2. create a new layer and make sure the layer’s blending mode is set to Hard Light

3. choose colours that are not too dark or saturated and colour in as a base. after you’re done, flatten the image (Layer > Flatten Image)

4. build your shadows! use a random darker colour and set the layer to Mutilply and the opacity to 50%

5. double click the background to unlock it and create a new layer underneath it. proceed to colour the new background layer (#eeeeee) and set Layer 0 to Multiply 

6. under Layer 0, start colouring the manga panel! make sure all coloured layers are set to Multiply

7. add these overlays and set them to Soft Light (these are the ones I use, but if you want to use different ones, go ahead!)

OPTIONAL!!

8. too add a gradient background, select the negative space around the characters, and create a new layer (make sure it is set to Multiply)