Playing recently the original BG1 I decided to import the portraits from BG2 so I can use them for my characters.  While exporting the portrait images I noticed that the BG1 portraits used in BG2 have been significantly brightened.  The new BG2 portraits are brighter overall than the BG1 portraits, which is probably why they decided to change the old portraits in order to "blend in" better with the new ones.  Upon comparing the images I decided that I was not quite happy with both the darker images from BG1 and the brighter images from BG2.  With some editing I was able to slightly change the brightness and tone balance for both sets of images and create a happy medium.  The changes are as follows:
 
BG1: The original portrait images have been slightly brightened while toning down some of the red and overall saturation.  The edited BG2 portrait images will be installed into the portraits folder so that they can be used for custom portraits.
 
BG2, BG1EE, BG2EE: The yellow tones of the BG2 portrait images have been slightly altered.  Sarevok's portrait will be installed into the portraits folder so it can be selected as a custom portrait.  An entry for it already exists in PORTRAIT.2da so if used by the player Sarevok in ToB will have MAN1 portrait.  BG1 portrait images will be replaced with the edited original ones from BG1.

After extracting the files to the BG1, BG2, BG1EE or BG2EE folder run Setup-BGx_CBPortraits to install.