Some important tips for blanching:
1. Make sure the water is at a full boil before you add the veggies.
2. Have enough water, or do not add too much veggies to where the water will take a long time to come back to a boil. Especially with green veggies, boiling water is key to retaining the green color.
3. Season the water. It should have the same salinity as salt water.
4. Have enough ice in your ice water bath. The faster you can chill the veggies, the better chance you'll have to retain their color and crunch. Certain veggies like carrots take longer to cool off because they are denser, and thus have a certain amount of carryover cooking even when submerged in ice water.
"Boldness has genius, power, and magic in it."
Johann Wolfgang Von Goethe