The asset tab controls the styling of a single asset added to this specific script. This is how to do it:
Go to the “Asset” section in the control panel to the right of the text
In the section, choose a Theme Effect or set it to Monochrome
The filter style can't be changed for a single asset in the script editor. Open the storyboard editor to finetune if needed. Open the document tab to change the filter for all your assets.