Passé composé v imparfait

Question

Please can someone explain why is this sentence in the passé composé instead of the imparfait ?"De plus, j'ai toujours adoré les couleurs des feuilles dans les arbres."

Cécile Janty-Davies · Accepted Answer

Bonjour Maria, 
When to use the passé composé and l'imparfait is sometimes difficult to justify, as it is so instinctive for native French speakers.
This is the sort of error that we never make!
The passé composé is used here because 'toujours' in a passé composé context means 'always (up until now)' — it describes a continuous state or habit that has existed throughout your past and continues into the present.
This differs from the imperfect tense, which suggests an ongoing state in the past that may no longer be true.
Compare:
J'ai toujours adoré = I have always loved (and still do) 
with 
J'adorais toujours = I always used to love (but maybe not anymore)
 
The passé composé with 'toujours' is essentially equivalent to the English present perfect with 'always' — it emphasizes the result or continuation of an experience into the present moment. 
J'ai toujours voulu visiter Paris = I've always wanted to visit Paris
Elle a toujours été gentille avec moi = She's always been kind to me