Is the default color for axis label black in RegionPlot?

I had no suspect that the default color for axis label and ticks would be black. However, after exporting an image to pdf, it seems that these colors are not black for me. Indeed, by checking the color with mspaint, the RGB value is (102,102,102).

The following is the code used to generate a plot:

cm = 72/2.54;
r = RegionPlot[x^2 + y^2 < 1, {x, -1, 1}, {y, -1, 1}, Frame -> True,
PlotRange -> {{-1, 1}, {-1, 1}}, FrameLabel -> {x, y}]
Export["test1.pdf", Show[r, ImageSize -> 7 cm]]


The following is the part of the resulting plot that I magnified:

It does not seem as the real black. Is it the expected behavior? How can I make the color "true" black, with RGB (255,255,255)?

• You can add the option FrameStyle -> Black, which also allows for other kinds of customizations, please see the Help. Jul 18 at 11:42
• @HansOlo Thanks, I checked that works. However, it is still very surprising to me that the default color is not black! Jul 18 at 11:47
• I think the default is Gray, at least in some recent versions of MMA that I have checked. Jul 18 at 11:48
• You can see the current default values on your system using CurrentValue[{StyleDefinitions, #}] & /@ {"GraphicsAxes", "GraphicsFrame", "GraphicsTicks", "GraphicsLabel"}. If you did nothing strange, they should all include the color specification GrayLevel[0.4] somewhere Jul 18 at 11:52
• Easier to read version of @Lucas Lang's comment. AssociationMap[ CurrentValue[{StyleDefinitions, #}] &, {"GraphicsAxes", "GraphicsFrame", "GraphicsTicks", "GraphicsLabel"}] // Dataset Jul 18 at 18:26

In addition to the comment Hans made about FrameStyle -> Black, I might also recommend using a Directive to thicken the frame like FrameStyle -> Directive[Black, Thick], if you really want a bold, black frame.
Looking at PlotTheme might also be useful. For example, you might be interested in PlotTheme -> "Monochrome".