JIRA uses three different colors, orange, blue, and green, to indicate how much time has been spent on a certain problem. To view this data, navigate to the ‘Time Tracking’ area.
Blue: The Original estimate is displayed using the color blue. This is an estimation of how long it will take to solve a problem. You can see the word 'Estimated' in this field.
Orange: The orange color represents the amount of time left to solve a problem. ‘Remaining’ is how this field is shown.
Green: The time actually invested in resolving the issue to this point is shown by the color green. You can view this field displayed as logged.