I agree with Joy...it could be dehydration/hydration...it could also be discolored due to a UTI or kidney infection which may cause blood to become mixed with the urine, certain medications can cause discoloration of the urine as well.
Mine seemed yellowish but its been light too. i found it smelt really harsh but it wasnt cuz it smelt more, it was my sense of smell was increased making me smell it more.
Your urine changing color is more likely a sign of hydration/dehydration.
I'm not sure of it being a sign of pregnancy but maybe about 2-3 months into my pregnancy my urine started changing to a more yellow color. It's not from prenatals since my first trimester they made me too sick to take.
I have not noticed any change in urine color since being pregnant aside from the prenatal vitamins I take ... after I take them my urine is really bright yellow for a couple of times after then it goes back to normal. But, I took the vitamins for months before I got pregnant and it had the same color. I do not think this is a sign of pregnancy.