short getFillBackgroundColor(); Color getFillBackgroundColorColor(); Do we want to continue to support both? With BorderStyle and FillPatternType, we no longer support short values.
Does short refer to an index into one of the tables defined in styles.xml? Can short be arbitrarily large (within file format limits) if there are a large number of styles, or is it a fixed quantity (only works for predefined quantities), which could be captured by a color enum or static class constant)? If so, this would be different BorderStyle and FillPatternType enums where the number is irrelevant (either a POI implementation detail or a format implementation detail).