If you have stitched for a while, can you usually pick out the DMC colors you need from memory when you go to your LNS? (For example, you know that 610 is a brown.)
I know of the top of my head what color 814, 3371, 413, 702, 221, 3740, 3363 are...and many more (maroon red, dark brown, grey, green, dark red, purplish pink, and a light forest green) Most of these # that I know by heart are ones I use frequently, and the more I think about it the more I realize I know, (930-932, 311, 3753, 745,....). But what I have in stock is constantly shifting and is pulled for various WIPs. So when I start a new project I have to go to my 3 boxes of wound floss first....These I "inherited" and since I do not like bobbins I use these first (as I use them up I do not replace them). Then I go to my stitchbow binders to finish off the list. If there is a list of 30 colors I am usually only missing 2-5 colors. I then try to think if I have any of these in a project already pulled....but I have to be careful there and usually just go buy it.
So to make a long answer to a short question even longer, No I do not just buy floss randomly based on memory of what I think I need when I go shopping, I only buy what I am missing from my stash. Which by the way is usually the higher newer #'s that DMC keeps adding Like 3865....did I mention I looks like white? Just what color were they aiming for here really?