I am working on updating several tables with Tableau's automatic conditional shading - dragging a measure onto the Color in the Marks card and selecting square for the Mark type, and having my Measure Values as the labels in the table.  I have noticed that sometimes Tableau very nicely converts the text color to white against darker shading backgrounds, but sometimes all the text stays black.  Any idea why this is hit and miss?  How can I make sure Tableau always auto-adjusts the text color based on the shading?