From Build 1233 on, you will be able to highlight segments of code in the Understand editor with custom color schemes, similarly to Notepad++.
1) Create new user styles in Tools -> Options... -> Editor -> Styles by clicking on the "New" button. Adding keywords is optional.
2) After creating the new style, change its background color to the desired color. These are now implemented as indicators and only the background color is respected.
3) After styles are created, they can be applied to arbitrary text ranges by right-clicking on a selected range and choosing one of the styles from the "Apply User Style" context menu (near the bottom). There's a "Clear" action to clear all user styles from the selected range.
You can save as many custom highlight colors as you'd like. Here I've used yellow and turquoise to highlight consecutive macro declaration sections:
