The 2014 revised edition of "What Does the Bible Really Teach?" uses the text of the 2013 NWT. I therefore assume this is the reason for the grey colour of the "Bible Teach" book.
Examples of the adjustments appear at pages 216 and 217 of the book:
(1) The revised text of Ezekiel 21:26, 27
(2) Use of "tree of enormous height" instead of "an immense tree", to match the change at Daniel 4:10
(3) Use of "1,260 days" instead of "a thousand two hundred and sixty days" to match the revision at Revelation 12:6.
Doug