>>>>>You DO know that #9 is 242,242,242 in windows version of acad?

No, color #9 in AutoCAD for Windows is 192,192,192 - the same as on Mac:

If you need to set colors in True Color (RGB), set it on True Color tab. When you switch between ACI and true Color tabs AutoCAD approximates colors, so this could be the case of the issue you see.

>>>>>Can I somehow manage the picture size in this forum? Same pictures seem to show up with different sizes...?

Yes, after you insert picture, select it and you will see buttons for adjusting image size: