Yes, fluorescent green wasn't the best choice for a grass background.
Honestly, I felt the background colors were really inviting. The only thing you want to do is make sure your tiles pop in whatever way is most salient to the player.
The purpose of graphics is to communicate information more quickly to the player. The more naturally the symbols of graphics are interpreted the more the player is drawn into the entire experience- because they don't have to 'read' the game- they 'feel' it and 'see' it and stuff like that.
However, if developers want a background color they can implement a background color if you just leave it transparent. I might want to represent day-night cycles via the background colors of grass tiles. It depends on your goal-- if you're making a set of tools or a comprehensive game aesthetic. Tools, leave the backgrounds transparent, otherwise, realize your creative vision.