Are there any Sefardic Poskim today that have written a book and discuss the Techelet? If so, can you bring one that is FOR the Techelet?
Rabbi Yitzchok Yosef states (resp. Rishon LeZion OC §1) that after some have concluded upon thorough examinations that we have today authentic techeles, if one wants to wear them [concealed] then there is an element of hiddur.
Rabbi Shalom Messas writes in a resp. dated from 2003 (Shemesh U'magen vol. 4 OC §24:3) that since the majority of rabbis do not wear techeles "since it is not extant" therefore it is better to refrain from putting on something that is certainly not techeles.
Rabbi Meir Mazuz discussed techeles in numerous lectures (transcribed in 'Bayit Neeman') and a couple of times answered questions regarding it in the pamphlet 'Peninei HaParsha'. He has said that on Shabbos he wears techeles on his talit gadol (and explains his practice that he does so because 1) it's fairly "new" and should be slowly broken into, and 2) if he wore every day it'd look as if he's speaking against earlier authorities who didn't wear at all). In another response (printed in the PH) to an inquiry if it's recommended to wear techeles, he replies that even though we aren't certain about its authenticity at least we know (today) 80% that it is and so when in doubt of a biblical commandment we are stringent.
Moreinu Rav Eliyahu Ben-Haim (Rosh Av Beth Din Queens and Rosh Yeshiva at YU) strongly holds of the Techeles, and he himself wears on his Tallit Kattan and Gadol.
On YUTorah you can hear many of his comments in regard to the wearing of the Techeles.
I could not find a source that tells you that a particular Rabbi says that Sephardim can wear Techelet, however there a plethora of websites which teach tying Tzitzit, both with and without Techelet, for both Ashkinaz and Sephard people. This seems to indicate that there is some sort of minhag which says Ashkanazim wear Tzitzit with and without Techelet and Sephardim wear Tzitzit with and without Techelet. Sorry I couldn't find you the actual source.