Writer table lines faint, grey colour, despite being set to black (version 6.2)

Hi there, I’m not sure why table lines appear a really faint, grey colour, regardless of their colour setting.
This only seems to occur when in the document; when printing, the colour of table lines appears as it should.

Anyone else had this issue? How do I fix it?

The LO version I used before this didn’t have this issue (version 4)…

Did you find the reason?