Squeak, some of them are YU people, but what’s the difference? I know people who learned in a Monsey Yeshiva, and got the okay from Rabbi Senter (chof-k) and Rabbi Rudinsky. I know people who live in Boro Park, Flatbush and Monsey who you’d consider “Yeshivish” (some are Chasidish) who wear techayles.
Having blue colored tzitzis does not make it posul. Please learn the halachos before going any further, as it is evident you don’t know enough to talk about the matter. I spent months just learning about tzitzis (not even about techayles) with a prominent Rav from Flatbush, who now has a Yeshiva in Lakewood.