When blue and yellow colours of light or paint are mixed in ordinary colour mixing, which resultant colour is typically observed?

Introduction / Context:
Basic colour mixing is frequently used in art, design, and everyday life. Children learn that combining certain primary colours produces secondary colours. This question asks what happens when blue and yellow are mixed, which is a classic example used in school level colour theory and general knowledge tests.

Given Data / Assumptions:
- We are considering ordinary colour mixing as in paints or pigments, not complex optical filters.- The two starting colours are blue and yellow.- We want to know the perceived resultant colour.

Concept / Approach:
In subtractive colour mixing, which applies to paints, dyes, and pigments, the primary colours are typically taken as cyan, magenta, and yellow, or in simple art teaching as red, blue, and yellow. When blue and yellow paints are mixed, the combination tends to absorb most red and blue wavelengths and reflects mainly green light, so the resulting colour appears green. This is why green is considered a secondary colour formed from blue and yellow in basic colour wheels used in art education.

Step-by-Step Solution:
1. Recall the basic rule from school art lessons: blue + yellow = green.2. Understand that both paints work subtractively, each absorbing some wavelengths of light.3. When mixed, the combination reflects wavelengths corresponding to green more than others, so the eye perceives green.4. Compare the result with the given options and identify green as the expected colour.5. Conclude that green is the correct answer.

Verification / Alternative check:
You can perform a quick practical check by mixing blue and yellow poster colours on a palette. The mixture visibly appears green, perhaps with slightly different shades depending on the exact pigments. Colour wheels and textbooks that describe secondary colours also list green as the colour produced by combining blue and yellow, which supports this answer.

Why Other Options Are Wrong:
- Black: Black may result from mixing many colours or complementary colours in large amounts, but simple blue and yellow typically give green, not black.- Red: Red is considered a primary colour in simple art teaching, not formed by mixing blue and yellow.- White: White is associated with adding light in additive colour mixing, as in combining red, green, and blue light, but blue and yellow paint do not make white.

Common Pitfalls:
Confusion can arise between additive colour mixing (for light sources) and subtractive colour mixing (for pigments). In additive mixing, different rules apply, but most basic exam questions assume simple paint like mixing. Remember that in everyday painting, the rule blue plus yellow equals green is widely taught and relied upon.

Final Answer:
When blue and yellow are mixed in ordinary colour mixing, the resulting colour is green.