The squares might be the same shade but the letters A and B are different colours, I think you differentiate shades by using the contrast between an object and those surrounding it so there is no direct way of comparing those two squares because the letters are different colours and the shadow means the surrounding squares are different colours too.
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CLUB inhabit a city in Middle England called Birmingham, their mission is to find amusing, diverting and character building activities with which to while away the time left before the last remaining member is dead. Joining CLUB is easy, leaving is - under some circumstances - even easier.
Squares
The squares might be the same shade but the letters A and B are different colours, I think you differentiate shades by using the contrast between an object and those surrounding it so there is no direct way of comparing those two squares because the letters are different colours and the shadow means the surrounding squares are different colours too.