In some cases someone else creates a block a little bit before you and gets it transmitted and accepted by the network before your wallet receives that block.
Meanwhile you had created a block and received a reward that turns out to be in an orphan block and thus not accepted by the network.
The wallet then marks it red as an orphan transaction.
It happens to everyone and it does not affect your holdings nor expected staking ROI unless you are getting more orphan rewards than rewards that stick, which would indicate a reliability issue with your internet connection or computer, or perhaps your system clock is not accurate (should be within seconds of the actual official time).
Also check that you are on the same block as our
block explorer. You can clear the orphan transactions with the "Tools" -> "Wallet Repair" -> "Recover transactions 1" tool.