From Mladen Rakic:

Basics:

The QQE (Quantitative Qualitative Estimator) indicator consists of a smoothed Relative Strength Index (RSI) indicator and two volatility-based trailing levels (fast and slow).

This version:

Compared to the original QQE indicator, this version is adding:

Discontinued signal line levels (to help further estimate the trend).
Color changing histogram (based on those levels).
This way we have more information available to analyze.

Usage:

You can use the color change of the QQE itself or the color change of the histogram as signals