Negative number test always fails

I'm running some javascript using p5.js and I'm stuck with these two conditions :

if( this.colour >= 255 )
        this.up = false;
    else if( this.coulour < 0 ){
        console.log("Ca yest !");
        this.up = true;
    }

and here is my problem : the following line never evaluates to true, even if this.colour is negative

else if( this.colour < 0 )

Where is my error ? thanks alot