Is the rainbow a bad sign?

ב"ה Shalom I don’t think it would be correct to say that a rainbow is a bad omen. I will try to give some perspective to the issue of a rainbow from the Jewish point of view. The Torah says "I have place my rainbow in the clouds and it shall be a sign of the covenant between Me and the earth…" (Bereshit 9:13) The Torah explicitly says that the rainbow shall be a sign that G-d will no longer bring a flood upon the earth. So, on the one hand the upside is that mankind will never see a disaster like the flood. On the other hand , it is somewhat a reminder of the bad ways of mankind in the past, therefore, we can perhaps refer to the rainbow as unpleasant memory. One of the commentaries (Redak Bereshit) actually looks at it in a positive way. He says, after all the rainbow is a natural thing which comes after each rainfall. Therefore, when people will see it they will not be afraid of a flood because of G-d's covenant. During the flood in the time of Noah the heavens were so dark nobody was able to a rainbow, so seeing it means this is not a flood. In the Talmud,(Ketubot 77b) it is mentioned that there were certain righteous people who in their days a rainbow was not seen, who due their great merit there was no need of reminders of the past. To sum up, it is not a bad sign in itself, but an unpleasant reminder. All the best