White Objects: Reflect all visible wavelengths equally. No specific colour is absorbed.
Black Objects: Absorb all visible wavelengths. No light is reflected to the eye, which the brain interprets as black (the absence of light).
Transparent Objects: Transmit all incident light. Very little light is reflected or absorbed, allowing objects behind them to be seen clearly.
Trace the Wavelengths: When solving problems involving coloured lights and objects, explicitly list which wavelengths are present in the source, which are transmitted by any filter, and which are reflected by the object.
The 'Black' Trap: If an object is illuminated by a colour of light it normally absorbs (e.g., a red ball in blue light), it will appear black, not purple or dark red. The object absorbs the blue light, and since there is no red light to reflect, no light reaches the eye.
Filter vs. Surface: Remember that filters transmit (pass through) light, while opaque surfaces reflect (bounce back) light. Do not confuse the two mechanisms.
Sanity Check: You cannot reflect a colour that wasn't in the incident light. A blue object cannot look blue if lit by pure red light.