/usr/share/labplot2/themes/GreyOnBlack is in labplot-data 2.4.0-1ubuntu4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 | [Theme]
ThemeName=GreyOnBlack
ThemePaletteColor1=220,220,220
ThemePaletteColor2=192,192,192
ThemePaletteColor3=169,169,169
ThemePaletteColor4=128,128,128
ThemePaletteColor5=85,85,85
[Axis]
LabelsFontColor=255,253,208
LabelsOpacity=1
LineColor=255,253,208
LineOpacity=1
LineStyle=1
LineWidth=3.52778
MajorGridColor=255,253,208
MajorGridOpacity=0.5
MajorGridStyle=1
MajorGridWidth=1.76389
MajorTicksColor=255,253,208
MajorTicksLineStyle=1
MajorTicksOpacity=1
MajorTicksType=0
MajorTicksWidth=3.52778
MinorGridColor=160,160,160
MinorGridOpacity=0.5
MinorGridStyle=3
MinorGridWidth=1.76389
MinorTicksColor=255,253,208
MinorTicksLineStyle=0
MinorTicksOpacity=1
MinorTicksType=0
MinorTicksWidth=0.283465
[CartesianPlot]
BackgroundBrushStyle=1
BackgroundColorStyle=0
BackgroundFirstColor=0,0,0
BackgroundImageStyle=1
BackgroundOpacity=1
BackgroundSecondColor=160,160,160
BackgroundType=0
BorderColor=0,0,0
BorderCornerRadius=0
BorderOpacity=1
BorderStyle=0
BorderWidth=3.52778
[Label]
TeXFontColor=0,128,128
[XYCurve]
DropLineOpacity=1
DropLineStyle=1
DropLineWidth=3.52778
ErrorBarsOpacity=1
ErrorBarsStyle=1
ErrorBarsWidth=3.52778
FillingBrushStyle=1
FillingColorStyle=0
FillingOpacity=0.4
FillingPosition=0
FillingSecondColor=0,0,0
FillingType=0
LineOpacity=1
LineStyle=1
LineWidth=3.52778
SymbolOpacity=1
ValuesColor=0,0,0
ValuesFont=Droid Sans,8,-1,5,50,0,0,0,0,0
ValuesOpacity=1
|