Hi @Anonymous,
Could you please share a bit more about your scenario?
Do you want to fill a Circle Icon control with RGBA code values (Red, Green, and Blue) from your Excel table?
Based on the needs that you mentioned, I have made a test on my side, please take a try with the following workaround:
The data structure of my Excel file as below (whose data has been formatted as a Table😞
Note: The Excel file stored within my OneDrive folder. On your side, you could consider save your Excel file into your OneDrive folder (or OneDrive for Business, Dropdox, etc), then create a connection to the Excel file in your OneDrive folder from your app.
The App's configuration as below:

Firstly, create a connection to the Excel file in your OneDrive folder from your app.
Add a Gallery control within your app, set the Items property to following:
ColorTable /* <-- On your side, you should type your RGBA code Excel table */
Within the Gallery, add a Circle control, set the Fill property of the Circle control to following:
RGBA(ThisItem.Rouge, ThisItem.Vert, ThisItem.Bleu, 1) /* <-- Rouge, Vert and Bleu are all columns in your RGBA code Excel table*/
Best regards,
Kris