What may be loud colour (3)
I believe the answer is:
hue
'colour' is the definition.
(a hue is a colour or complexion)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for hue that I've seen before include "Delicate shade" , "red or black, say" , "General outburst of alarm or protest - . . . and cry" , "Colour or tint" , "Cast" .)