If the same red poster colour appears different in different shapes, which effect should be considered first?

Correct answer: The visual effect of surrounding colours, value, and area size

Colour perception is contextual: the same red can look brighter, duller, warmer, or darker depending on neighbouring colours, their lightness or value, and the size and shape of the coloured area. Option B correctly identifies these visual influences. Changing the colour name does nothing, while brush price and container size do not alter the perceived colour relationship in the finished poster.