Okay - the best practice for managing the detailed look of a report, including the colors, is to put the report on a dashboard and then edit the dashboard settings. As you point out, you can find the settings for a simple XML dashboard here and more detailed charting settings here.
If you really want to change the look of a report that is not part of a dashboard, you will need to mess with the viewstate. This is not the recommended practice, and it is not well-documented. But if you take a look at savedsearches.conf and viewstates.conf in the manuals, you will see that the viewstate often seems similar to the chart settings in views. Each saved search may have a corresponding viewstate.
Most of the time, the viewstate is created/updated when the user creates/updates a report using the report builder. If at all possible, this is the best way to do things if you aren't putting the report on a dashboard.
However, after you have set everything that you can via the report builder, you can manually edit the viewstates.conf file. The weird names and numbers in the viewstates.conf file, such as "FieldPicker_0_6_1" refer to the advanced XML modules that make up the view. To figure out these numbers, add ?showsource=true to the end of the URL when you are looking at the report. At this point, you are embarking on a real voyage - I recommend that you learn all you can about advanced XML before you get too far. Be prepared to invest days, not just hours. (Now you see why best practice = use a dashboard.)