The charting.fieldColors works great when you know all the names of the fields, but isn't always your best choice when you don't the field names in advance. Try one of these two options:
Option 1: Use seriesColors instead of fieldColors, like this
<option name="charting.seriesColors">[0x00FF00,0x999999,0x1e93c6, 0xf2b827, 0xd6563c, 0x6a5c9e, 0x31a35f, 0xed8440, 0x3863a0, 0xa2cc3e, 0xcc5068, 0x73427f]</option>
Which should make the first field green, the second field gray, and then the next fields (if any) the standard Splunk colors: blue, yellow, etc.
Option 2: Or you could use fieldColors, but name all the fields
<option name="charting.fieldColors">{"OK": 0x00FF00, "Other": 0x999999}</option>
To give the Other field a specific color. (You may need to change the capitalization of the field name to match the pie chart output.)
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