you turned on "Style Override Highlighter", a feature new to InDesign CC 2015.3 that would indicate if there is a difference in between the used character style or paragraph style and the actual formatted characters or the whole paragraph.
You can turn it on/off eg. in your Paragraph Styles Panel or your Character Styles Panel.
Btw. The blue bar at the edge of your text frame is indicating an override of the whole paragraph.