In my Juptyter notebook I have many horizontal rules (generated in markdown cells) to break up the blocks of code, to create the horizontal rule I am using 3 underscores "___". For some reason, which I cannot figure out, the line sometimes appears as dark grey and sometimes as light grey.
In the screenshots below you can see the same "___" produces two differently colour lines.
Does anyone know the reason? Ideally i'd like them all to be the darker grey

