See page 376 of your instruction manual.
It's not an indicator that there is a "problem" -- it's merely an alert to tell you that you've set one of four possible things:
1) you enabled monochrome mode (so you wont get a color image)
2) you've applied a manual white balance correction (so you might not get the color fidelity you were expecting)
3) You've enabled ISO expansion mode (so you may have high-noise in your image.)
4) You enabled "spot" metering (so you may not get the metering you expected.)
If any of these four conditions are true, then the alert icon will appear -- just to call your attention to the fact that you might not get the results you were expecting. Obviously there are times when you might deliberately WANT to do one or more of these things -- so it's not an indicator of a "problem", but rather the camera is trying to get your attention in case you did this some time back... and forgot to revert camera settings to more standard behavior.
Tim Campbell
5D III, 5D IV, 60Da
