Fig. 2: The Density Scatter Plot results show the XGBoost-predicted wind speeds against the observed wind speeds based on the 20% testing sample.
From: Unveiling multiscale drivers of wind speed in Michigan using machine learning

The coloration represents the density of the points based on equal-size hexagons, and the density of the scatter points represents how the data is clustered in the observation/prediction space. a Density Scatter Plot of Predicted vs. Observed Wind Speeds for all seasons. b Density scatter plots of observed vs predicted values by season.