What does this pattern (由 … 而) mean, exactly?
由 is "from"/而 is "and then". 由X而Y is used to described a continuous evolution (verb Y) from one state (noun X) to another.  Per your own example it is an evolution from being white to turning red (红 is being used as a verb here).

Notice how you inserted the verb 到 in your second sentence: you would need to add “至" in the first sentence to make it roughly comparable (though it seems weird to say 而至 here, though perhaps only because the register is too formal).  In that case, X is 星期一 and Y is 至: 星期二 can't be repurposed as a verb like 红 can.