Problem with Treemap

arouillard,

By default, the lowest value in your data is mapped to the least saturated color, and the highest value to the most saturated color. Center value is just the arithmetic mean of Minimum and Maximum, not all values. You may set them manually through Data colors section in Format pane.

https://powerbi.microsoft.com/en-us/documentation/powerbi-service-tips-and-tricks-for-color-formatting/#customize-the-colors-used-in-the-color-scale

As an alternative, use SIGN Function to create a calculated column.

Color Saturation Flag =
SIGN ( Table1[Column3] - AVERAGE ( Table1[Column3] ) )