Slitherine

Seems all my provinces have range 8 atm, even Cartage which has 8 in bonus from buildings and modifiers.

ps. why are some of the trade range 8's blue?

That's a limitation on purpose indeed, partly to not use too much CPU, partly to not have a too easy time with trading range reaching half the map.
Blue means you are capable of maritime trade, because water is blue. Except it is not. Well, you get what I mean!