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How to set the cell color to a user defined value using NPOI from F#?

As far as I can tell (from F# at least), cell can only be colored using predefined `NPOI.SS.UserModel.IndexedColors`. From the available methods / properties,

```
val it: ICellStyle =
  NPOI.XSSF.UserModel.XSSFCellStyle
    { ...
     FillBackgroundColor = -494s;
     FillBackgroundColorColor = NPOI.XSSF.UserModel.XSSFColor;
     FillBackgroundXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     FillForegroundColor = 64s;
     FillForegroundColorColor = null;
     FillForegroundXSSFColor = null;
     FillPattern = NoFill;
    ...
```

only `FillBackgroundColor`, `FillForegroundColor`, and `FillPattern` can be set to an `int16` value, which corresponds to the `IndexedColors` values, and the rest of the patterns are immutable. I can create a custom

```
new NPOI.XSSF.UserModel.XSSFColor([|255uy; 192uy; 150uy|])
```

color, but I simply couldn't figure out yet how to assign this either to an existing cell style or to a brand new one. All the articles I could find also only use `IndexedColors` (e.g., [1](https://www.baeldung.com/apache-poi-background-color), [2](https://stackoverflow.com/a/58475635/1498178), [3](https://stackoverflow.com/questions/37052352/how-to-change-cell-color-with-npoi), ).

Am I missing something obvious or this is indeed not possible?

<sup>The meaning of the terms "foreground" and "background" in this context is also misleading, but that is inherited from Apache POI, and it is well documented online (again, [here](https://www.baeldung.com/apache-poi-background-color) and [here](https://stackoverflow.com/a/58475635/1498178), for example).</sup>

---

**edit**: Found two other solutions for C# ([this](https://stackoverflow.com/questions/55514395/is-there-any-way-to-add-color-to-cell-from-hex-value-like-72fe9c-in-my-excel) and [this](https://stackoverflow.com/questions/65245153/npoi-set-cell-color-to-a-custom-color)), that do the obvious by setting `FillBackgroundColor` to with a custom `XSSFColor`, but, again, I couldn't figure out how to do this in F#:

```
> cs;;
val it: ICellStyle =
  NPOI.XSSF.UserModel.XSSFCellStyle
    {Alignment = General;
     BorderBottom = Thin;
     BorderDiagonal = None;
     BorderDiagonalColor = 8s;
     BorderDiagonalLineStyle = None;
     BorderLeft = Thin;
     BorderRight = Thin;
     BorderTop = Thin;
     BottomBorderColor = 64s;
     BottomBorderXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     DataFormat = 0s;
     DiagonalBorderXSSFColor = null;
     FillBackgroundColor = -494s;
     FillBackgroundColorColor = NPOI.XSSF.UserModel.XSSFColor;
     FillBackgroundXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     FillForegroundColor = 0s;
     FillForegroundColorColor = NPOI.XSSF.UserModel.XSSFColor;
     FillForegroundXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     FillPattern = NoFill;
     FontIndex = 3s;
     Indention = 0s;
     Index = 43s;
     IsHidden = false;
     IsLocked = false;
     LeftBorderColor = 64s;
     LeftBorderXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     RightBorderColor = 64s;
     RightBorderXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     Rotation = 0s;
     ShrinkToFit = false;
     TopBorderColor = 64s;
     TopBorderXSSFColor = NPOI.XSSF.UserModel.XSSFColor;
     VerticalAlignment = Bottom;
     WrapText = false;}

> c;;
val it: XSSFColor =
  NPOI.XSSF.UserModel.XSSFColor {ARGB = [|255uy; 255uy; 192uy; 150uy|];
                                 ARGBHex = "FFFFC096";
                                 HasAlpha = false;
                                 HasTint = false;
                                 Index = 0s;
                                 Indexed = 0s;
                                 IsAuto = false;
                                 IsIndexed = false;
                                 IsRGB = true;
                                 IsThemed = false;
                                 RGB = [|255uy; 192uy; 150uy|];
                                 RGBWithTint = [|255uy; 192uy; 150uy|];
                                 Theme = 0;
                                 Tint = 0.0;}

> cs.FillBackgroundColor;;   
val it: int16 = -494s

> cs.FillBackgroundColor <- c;;

  cs.FillBackgroundColor <- c;;
  --------------------------^

/Users/toraritte/dev/clones/dotNET/slate-excel-reports/stdin(332,27): error FS0001: This expression was expected to have type
    'int16'    
but here has type
    'XSSFColor'    

> cs.FillBackgroundColorColor;;
val it: IColor = NPOI.XSSF.UserModel.XSSFColor {ARGB = null;
                                                ARGBHex = null;
                                                HasAlpha = false;
                                                HasTint = false;
                                                Index = -494s;
                                                Indexed = -494s;
                                                IsAuto = false;
                                                IsIndexed = true;
                                                IsRGB = false;
                                                IsThemed = false;
                                                RGB = null;
                                                RGBWithTint = null;
                                                Theme = 0;
                                                Tint = 0.0;}

> cs.FillBackgroundColorColor <- c;;

  cs.FillBackgroundColorColor <- c;;
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^

/Users/toraritte/dev/clones/dotNET/slate-excel-reports/stdin(334,1): error FS0810: Property 'FillBackgroundColorColor' cannot be set
```