Note that this does not affect VIs that you have already created. These options under the Environment category are shown here:
There are two ways to change the block diagram of Existing VIs. You can accomplish this manually or programmatically.
To accomplish this programmatically, there is a block diagram property that can be edited to change the background color of an existing VI.
Collaborate with other users in our discussion forums
A valid service agreement may be required, and support options vary by country.