The use of shading in figures is allowed provided this assists in their understanding and is not so extensive as to impede legibility.
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/a_ix_7_2.htm
Date retrieved: 17 May 2021
Source: http://www.epo.org/law-practice/legal-texts/html/guidelines/e/a_ix_7_2.htm
Date retrieved: 17 May 2021