Intensify colour, nothing blue strangely (8)
I believe the answer is:
redouble
'intensify' is the definition.
(I know that redouble is a more specific form of the action intensify)
'colour nothing blue strangely' is the wordplay.
'colour' becomes 'red' (red is a kind of colour).
'nothing' becomes 'O' (looks like zero - 0).
'strangely' indicates anagramming the letters.
'blue' anagrammed gives 'uble'.
'red'+'o'+'uble'='REDOUBLE'
(Other definitions for redouble that I've seen before include "Bid" , "increase fourfold" , "Bridge call" , "Produce more" , "Be louder to multiply by four - say degree of effort" .)