Light blue with tassel

Hello Rabbi,
I want to cast a thread of blue thread on a tzitzit from a doubt. I saw in Rabbi Yitzhak Yosef’s Yalkut Yosef that it is not advisable because the great men of Israel in the last generation did not cast a thread of blue thread. You probably do not agree because you have researched the issue. I have not researched and am wondering if he is right or if I should cast a thread of blue thread from a doubt in Torah.