speaking of readability, you are using pixelated font, but unfortunately vx ace has built-in anti-alising for fonts, so font will be blurry anyway. but i think i found pretty good solution to increase readability in this game:
set default outline to true,
add this string to main script:
Font.default_out_color.set(Color.new(255,255,255, 125))
#values could be ajusted
and decrease tone of your green, yellow, blue etc. in window.png
something about #588a00, #aa7700, #0073b5 respectively.
edit:
well, actually readability could be fixed even without adding outline, just by ajusting tone color of font.