I wanted to add a reply, listing the things I specifically don;t like about the grid, hoping it'll prompt someone to tell me which CSS setting to override. The huge nesting compexity of the styles themselves do not make it very easy to get these things looking how I want, especially without affecting other things.
1. I strongly dislike the light gray border color
2. I strongly dislike the light gray background on the column headers
3. I strongly dislike the gray color of the filter row
4. I strongly dislike the padding in the cells and rows of this grid
5. I strongly dislike the padding in the column headers
6. I strongly dislike the whole filter row altogether. The colors, the padding, the size of the components...
7. Did I mention how much I strongly dislike the light gray color, everywhere. The icons, the text, the borders, the backgrounds...