I'm feeling blue. What does that mean? If I look up the idiom definitions for "feeling blue" it covers an emotional stage where you are feeling unwell, mainly associated with depression or unhappiness.
Loosing a job can make you feel blue. Loosing a love one like wise. So of course there are grades to associate with feeling blue. IMO feeling blue is a mild temporary stage initiated by us leaving our comfort zone.
What is the opposite of feeling blue? Looking into color theory an "opposite" color is a complementary color, that when mixed with its counterpart produces either white, black or grey. The complementary color to blue is yellow.
If I google "feeling yellow" it means many things - the main is feeling cowardly. If you are feeling green then you are feeling envy. I'll stop pondering over this subject. It is none conclusive.
I just like the color blue - so I don't mind "feeling blue". I my vocabulary it is associated with a stage where there are more opportunities than challenges and where I really have the chance to change course. This evokes uncertainty and anxiety - but in a positive way.