You can display a graph (i.e., histogram) in VueScan below the tabs via Image ‣ Graph. It is not visible in Guide me mode. Depending on your choices, it will show different graphs.
This graph shows the uncorrected (gamma 1.0) curves of RGB color and the infrared channel. The histogram curves of the RAW file will not change when you configure settings in the Color tab.
This graph shows the black-and-white points in the histogram. You can configure them here manually by pulling the triangular sliders below the curve. The curves of the histogram displayed in the background will not change when you configure settings in the Color tab.
This option basically resembles the Curves option in Photoshop. In Photoshop, Curves ...