Thank you. I actually Found it under scene, color management, false colour.
This scale varies if I modify the exposure. If I leave the exposure at 1, I still get a blue color for the lux of the sun which usually translates as 250 lux which is not enough for direct sun lux. What am I doing wrong here?
Your screenshot is super tiny.
But it appears you are using some false-color mode built into Blender. I don't know how that behaves, but it's not what Dade meant.
Also, make sure to set the sun and sky gain to 1 for your use case.