Opened the image
Checked and saw it was already in RGB
Selected the front Mushroom cap with magnetic lasso and used adjustment layer to colorize to red.
Did the same to the next and changed it to green.
Added some sprites to the image on their own layers and arranged them
Selected the next Mushroom cap and saved the selection as Mushroom Cap Side
Changed that one to teal
Repeated with the rest of the Mushroom caps
Used a Custom Gradient layer with overlay on one cap
Crystalized one cap
Paint Dabbed another
Dark Stroked another
Ink Outlined another
Made a poka-dot image and used a vector mask to restrict it to a mushroom cap
Created one as a Stroked and Filled path
Selected the tree and did a hue/saturation adjustment to make it brown
Did the same with the bottom of the Mushrooms
Painted remaining picture brown at 50% opacity
Flattened Image
Autocolored to adjust contrast and balance