Use the Gradient to create an effect based on colours and patterns of your choosing.
To access the Gradient menu, use:
Batch, then select a node from the Node bin.
Timeline, then use Batch FX (see Creating Batch FX).
Tools, then select from the menu (See Accessing Tools).
The Modular Keyer, then select a node from the Node bin.
This node accepts a front and matte clip, and outputs a result and outmatte.