Colors changing

i have noticed lately that when i scroll through messages in my inbox the color changes. i only use bold blue for unread and regular blue for read messages. yet, somehow purple appears when i scroll up or down on previously blue messages. see screenshot -- i had clicked on the Amazon email so it became blue after that -- but two purple won't turn blue until i click on them -- even though i've previously read them. is this a mail thing or a Snow Leopard thing AND does anyone know why this is happening?



Message was edited by: jayhawk