Unwanted colouring of imported <table>'s [#2528258]

When including html imported from a file or just typed by hand to create a content page then the theme imposes colouring on the

elements throughout the file. The colouring seems to be the same as the unselected menu selection tabs, which in my case turn out to be faint pink or grey. The result is that each nested table gets more colouring, looking rather like the stepped pyramid in Eygpt.

To see this, create a new content page, choose the "html" editor, add a table with a couple of

's having a bit of random text. For good measure after the table add a

with text content and some plain text. Save. View. The table portion is coloured, the div portion is not.

The result of this is imported html files are coloured, often to a very annoying degree, making use of

's impractical and thus prevents using most imported web files.

Two screen captures are attached, showing in the first a section of the final web page, and in the second an editor's view of the file construction. The entire background should be white/unchanged from what I inserted.

Curiously, as I type this message the screen shows the same pink area covering. That appears to be the same effect as I am discussing. It is unwanted.

The test situation at hand is Panopoly/current, using responsive Bartik or ordinary Bartik themes.
Changing to non-Bartik themes removes the effect.
What is wanted is no colouring, and no

outline framing lines and similar.