Is there a tool that can reference colors?

You can do tonal correction by going to Edit > Tonal Correction > Color Match.

Note:
From March 14, 2024, Clip Studio Paint Ver. 3.0.0 now has Color Match.
Update to the latest version here.

Steps

If you are using Clip Studio Paint on tablet or smartphone, please switch to Studio Mode first.

1. Select the layer you want to color correct.

Note:
If there are multiple layers that you want to color correct, then merge the layers first.

2. Select Edit menu > Tonal Correction > Color Match.

■ PCs and tablets

■ Smartphones

3. Select the image or gradient you want to use for Color Match.

4. The colors on the layer will change according to the image or gradient used.

For detailed information on Color Match, please refer to the following article.