How do I get the green red and blue blocks

I'll assume you've already done the Yellow Switch Palace.

To get to the Green Switch Palace, you must find the second exit from Donut Plains 2. To get that, in the first section, just before the second Dragon coin, you want to allow the tan block to rise to the gree pipe above. Just before you get crushed, enter the pipe. Head right. You'll see a series of ascending regular blocks. Use them as steps. Try to hit the rightmost and thus highest block from beneath to cause a vine to appear. Climb the vine and find the key and keyhole.

To get to the Red Switch Palace, you must find the secret exit from Vanilla Dome 2. You'll find that by following the only path until you make your second surfacing, just below the second Dragon coin. Head left. DO NOT USE THE 'P' SWITCH YET. Clear the vertical line of coins to the left. Pick up the 'P' Switch and carry it near the wall of brown blocks. Activate the Switch and plow through the wall of coins, jump the first gap and dive through the next block of coins and aim for the left wall. Try to catch the ledge. If you miss, just swim under to the left. There, you'll find a Key, Dragon coin and the keyhole.

I'll leave the Switch Palaces to you.

Forgot to add one:

To reach the Blue Switch Palace, you'll need the secret exit from Forest of Illusion 2.
To reach the secret exit, after you pass the Midway gate, proceed above and right, until you go down. When you see a '!' block head left. Yes, I KNOW it looks like a wall, but...you'll swim tight through it. The Key and keyhole are on the other side.