yes and no on having issues when mixing them..the old style green when mixed with red would gel. a lot of the newer greens on the market now supposedly won't, but that doesn't mean all the different brand greens won't.
is your block all aluminum? if so, i'd stay with the red as it's made for them. if it's a mixed block (part alum/part cast) then go green.
ige tlca #1431