What was the extent of Lavan's efforts to gain at Yaakov's expense?
Ramban: Following the initial agreement, that Yaakov would receive the spotted and blotched sheep and goats and the reddish-brown sheep, he began changing the conditions annually, when he saw the extent of Yaakov's successes.
How could Lavan say, "your wage will be the dotted ones"? They already agreed that Yaakov gets the dotted and blotched!
Moshav Zekenim: Yaakov stipulated that Lavan may choose each year to give to him dotted, blotched or Akudim.
Why does it say "Im Koh Yomar" in the future?
Ramban, Ohr ha'Chayim: Lavan changed the conditions after the animals were already pregnant - but to no avail. Hashem took into account what Lavan will say, and formed the seed inside the mothers in Yaakov's favor. Ha'amek Davar - this shows that my success is not due to the sticks. At the time I put sticks, I did not know what Lavan will say later!
Malbim: Lavan changed the conditions right before the animals were born, after they were already formed. Hashem changed the color according to what Lavan will say.