This month we added the ability to format text fields based off a numeric field: https://powerbi.microsoft.com/en-us/blog/power-bi-desktop-may-2018-feature-summary/#conditionalFormatting
We also are planning on adding a feature that will let you format your text based on comparisons. I’ll update this idea based on our progress on that feature.Vincent Pray commented
Have wanted this for so long! PBI dev - check out Dev Express for conditional formatting ideas - best functionality for this I've ever seen.