Minecraft wiki entry for Command_blocks_and_functions, associated text: Using /say @p, the command block can report the nearest player. If the command block is placed after a finish line, it will say the finishers in order. Players can also do /tellraw @p {"text":"THIS IS A MESSAGE"} and when activated the message "THIS IS A MESSAGE" will come up on the chat system. Players can also color the text using "color" at the end of the next command /tellraw @p {"text":"THIS IS A MESSAGE","color":"green"}.