This article may answer your "Import" question-
Several things can affect "Export" photos- Monitor calibration, Photo embedded profile, etc.
Supply more details of your workflow, will help you get answers.
If these are RAW photos, then it is expected that their appearance will change shortly after import. What happens is that Lightroom first displays the JPG preview that is in the RAW file, and then after a few seconds, Lightroom renders its own version of the RAW image, which will be different than the JPG preview. There is no way to turn this off. You then have to edit the RAW photo in Lightroom to make it appear the way you want.
When you export are you selecting File Format to be JPG or TIF and Color Space to be sRGB?
Please provide details ...
When you import, they look different to what?
When you export, they look different to what?
How are you viewing the exported files?
Do you work with raw files or jpgs?
What version of Lightroom?