Hi @Anonymous ,
Do you want to change the Column Header color and font size within the Data Table control in your canvas app?
Based on the needs that you mentioned, I think the HeadingFill property and HeadingSize property of the Data Table control could achieve your needs:

On your side, you could change the HeadingFill property and HeadingSize property value of the Data Table control to achieve your needs as above screenshot mentioned.
In addition, if you want to change the color and font size within the Data Table body, I think changing Fill property and Size property of the Data Table control could achieve your needs.
Best regards,