hovertemplate = "<b>%{y:.0f}</b> "+"<extra><b style='color:black;'>"+ customName + "</b></extra>"
Within a trace’s properties, you can customize the hovertemplate. If you use the extra tag, it will allow you to customize the field you are looking at. I haven’t figured out a way to control the text’s color without changing its style to bold yet, but I use the “b” tag which makes the text bold and set the color to black within this tag.