For setting circadian rhythm, what defines "blue light"?

Blue light is defined as being between 380 nanometers and 450 nanometers.
I wouldn’t go with direct light in your eyes; too damaging. Maybe diffused?

They sell lights that mimic the sun; you might want to just go and buy one of those.

Why not just buy some blue Maui Jims?

OMG safety first ok ?!
you do NOT want to put LEDs that close to your eyes please do NOT try that with any color LEDs (even “IR”, some are close enough to our visible spectrum they will could doom the subtle parts of your night vision)! It is not that they put out so much total light but all the light it puts out comes from the eensy weensy tiny winy emission zone of the diode and that intensity Can Toast Your Peepers like looking at the sun !!
If you want to try anything like anything like that (sic) use substantial diffusers to spread it out to an even glow with no hot spots.

It’s not advisable to shine any manner of light directly in your eyes. As Nullo stated, there are lights designed to mimic the light blue hue produced during the daytime. Those are your best bet.

I use melatonin tablet to reset my rythm in my frequent time zone changes. I also find it harder to adjust when I go from west to east rather than east to west. I don’t like the idea of shining lights into my eyes and suspect that it will be harmful, in the long run.

What I do is try to stay awake in the new zone and go to bed at my regular time, 11:00 PM, and take a couple melatonin tablets before I go to sleep. The jet lag usually is gone the next day.