Sorry for that, I guess I missed the questions at the end.
For the arrow color, you will have to go into the PowerGallery100/galleries/ribbon_fullsize/images and change the image itself to be the colors you want.
To change the gray bar, you would look in the light.css file and change the css block:
.pg-rf .title
To change the text in the gray bar, you would look in the light.css file as well and change the css block:
.pg-rf .title .fullsize-title
To change the size of the thumbnails in the scroller you would have to go into the PowerGallery100/galleries/ribbon_fullsize/index.php file and find this line of code (should be line 80 if you haven't made any changes):
echo '<img alt="" title="' . $i . '##' . str_replace('"', '\"', $gallery['images'][$i]['title']) . '##' . str_replace('"', '\"', $gallery['images'][$i]['description']) . '" src="' . $gallery['images'][$i]['thumb']['url'] . '" width="62" height="62" />';
change the width and height there and the thumbnail should be different sized.