I HAVE ALWAYS HEARD THAT GREYS GROW INTO YELLOWS. I DON'T KNOW ABOUT ALL, BUT I DO KNOW ABOUT ONE. I LEFT ONE THE OTHER DAY AND WENT BACK 4 DAYS LATER AND IT WAS 3 INCHES TALL AND LIGHTER YELLOW COLOR. BEFORE THAT IT WAS NOT EVEN AN INCH TALL AND GREY IN COLOR. I AM SURE IT WAS THE SAME SHROOM.