tosafos could go like the gra since in succah he makes it machlokes bavli and yerushalmi and in chulin is sosem blue.
mareh painm learns it is a machlokes (even if you think it is shver that’s how he learned) so the klal is machlokes bavli vyerushalmi halacha kibavli. besides when it comes to the gra you have to find rishonim who disagree not achronim.
the akeidas pshat doesn’t requuire different madreigos in color – it could be different madreigos in the zechira- i. e. lfi the shla the bechina of kriyas yam suf can bring to the bechinah of matan torah
about several midrashim saying asavim the radziner writes since this medrash is brought 3 times in bavli and in sifri and in medrash raba and tanchuma and all those places don’t say it than we can assume the ikar girsa in the medrash is without it.
see http://hebrewbooks.org/pdfpager.aspx?req=41254&st=&pgnum=27&hilite=