Colored Signs appears darker in North and South

If a Sign with color is created, the colored Signs text appears darker.

Used Commands:

North:
setblock ~ ~2 ~ minecraft:wall_sign 3 replace {Text1:"{text:\"Text\",color:dark_green}"}

East:
setblock ~ ~2 ~ minecraft:wall_sign 4 replace {Text1:"{text:\"Text\",color:dark_green}"} EAST

South:
setblock ~ ~2 ~ minecraft:wall_sign 2 replace {Text1:"{text:\"Text\",color:dark_green}"} SOUTH

West:
setblock ~ ~2 ~ minecraft:wall_sign 5 replace {Text1:"{text:\"Text\",color:dark_green}"} WEST