The Fluid Grid is the same as a regular Grid, but is used for viewing fluids in the fluid storage of your storage network.
To insert a fluid, players can shift click on a fluid container like a bucket in their player inventory while in the Fluid Grid GUI.
The player can also click the fluid container in the GUI to insert it.
Players can extract the fluid by clicking on it. The Fluid Grid will then fill a bucket with the selected fluid.
Refined Storage will first search an empty bucket in your inventory. If none is found, a bucket will be searched in your storage network.
Some fluids cannot be filled in a bucket, then the only way to extract those fluids is by using an Exporter.
You can recolor the Fluid Grid in 2 ways:
Using a dye on the Fluid Grid
Combining the block with a dye as a crafting recipe