export jpeg is dull compared to app screen why?

MAybe your work color mode is different than windows. If you work for example in RGB  in rebelle but your windows screen is in SRGB.

IT happened to me that way so then your windows image viewer open the file in a different color mode and your art can look either flushed or more colorfull .

try opening your saved jpeg in rebelle if colors comeback then it is your windows color mode that need to be changed, if the jpeg is still flushed out in rebelle then there is a conversion problem, maybe you lowered the quality of the picture when you saved.

Is the a setting in Rebelle?

So it is definitey the RGB  setting.  I am getting closer. How do I get the color mode of the application to exactly match the color mode that is exported?

I figured it out. Set default Windows to same color management in Rebelle.  Thank you so much!  I would have never figured this out.