So yea, I've been using pentel graphgear 1000. I have all 4 collection, .3mm, .5mm, .7mm, and .9mm. Anyways .7 and .9 are filled with blue and red lead. My .3mm is using black lead. So I'm looking for another color for the size .5mm but I can't find any at that size other than blue and red! Does anybody know where I can buy another lead color? possibility green or orange?

You may have to order them online from an art supplier. Or try a good office supply store locally.