verbs - Contradictions in the same sentence

Consider the following example:

This paper will turn red rather than blue which is her favorite colour.

What colour does she like, red or blue? Is there a comma missing after blue? Will adding it solve the confusion? Also, are sentences like these used in written English?

Are turning red and turning blue verbs in the sentence and colour the object?

Answer

Generally modifiers, or modifying phrases, come right after or right before the word they modify.

Adding the comma makes things clearer and makes the sentence seem a bit less like a "run-on" sentence, though in speech you probably won't hear a distinct pause between "blue" and "which."

This paper will turn red rather than blue, which is her favorite colour.

So "blue" is her favorite color, because "which is her favorite color" comes right after "blue."

Something similar you might hear/read:

This paper will turn red rather than her favorite color, blue

To say red is her favorite color:

This paper will turn red, which is her favorite colour, rather than blue.

Omitting the commas here would definitely be awkward.

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Putting comma right before rather?

This paper will turn red, rather than blue which is her favorite color

Nope, this doesn't really change the meaning of it. It just slightly more emphasizes the fact that the paper will turn red - emphasizing "This paper will turn red" as the main idea in the sentence.