1. First Purple Coin
Hit the Yellow Switch located at the lower right corner of the screen.
Once the platforms are available, move up to the fifth level of platforms with a single box on the left to get the first Purple Coin.
After getting that, enter the green door at the bottom. If the door disappears, hit the Yellow Switch again.
2. Second Purple Coin
To get the second Purple Coin, just pass through the first “invisible” coin you see located at the lower right corner of the screen. After passing through, the second Purple Coin will reveal itself. Just pass by it again to get the second Purple Coin.
3. Third Purple Coin
To get the third Purple Coin, move up to the top and then hit the P Switch on top to turn one Boo into the third Purple Coin.
After getting the coin, enter the green door to the right.
4. Fourth Purple Coin
Before getting the fourth Purple Coin, move up to the third level of platforms and hit the Yellow Switch to reveal the other platforms.
After that, hop on the second row of bricks and jump under one of the bricks beside several Surprise Question Blocks to get the fourth Purple Coin.
5. Fifth Purple Coin
To get the fifth Purple Coin, head to the highest level of the platforms and make a high jump from the left most corner of the screen to get the fifth Purple Coin.