/tellraw (using text,color,bold and extra) results into unknown error

I was making a tutorial map and wanted to use /tellraw (as I like colored text ). I was using a Commandblock with this command: /tellraw @p[team=Player1] {text:"You are violating the ",color:gray,bold:true,extra:{text:"RULES",color:yellow}}. I was in team Player1 when I activated this
Commandblock, but nothing happened so I checked the output of the Commandblock and it said "[08:56:54] An unknown error occurred while attempting to perform this command".