I've made about four pair in the last couple of days, in stripes and plain colours, but the light is a bit bleak for taking photos indoors, what with all those lovely big, fat rainclouds gathering outside. So these are the only pictures worth uploading.
These are an easy make; you basically just trace a pattern from an existing pair of leggings, cut them from your tee and sew them up. I was going to write a tutorial for you, but the official excuse is, as already mentioned, the light for snapping pictures indoors is way too grouchy. Moreover, my lovely one-year-old cyclone of a daughter busted my chops today (not literally, albeit she is the type to do so literally, though always with a smile!), and after cleaning up that mess, I am in the mood for being bone-lazy. Luckily, there's already a great tutorial here, with easy instructions and lots of lovely, sunny-day type pictures, so there's no need for me to write one - hooray!
And, if you don't have many stretchy tees, hit the local op-shops and see what you can find. There must be scores of different shades and patterns out there! I found a rather loud t-shirt with stripes in two shades of hot pink, grey and blue, which should make for a pair of legs that are very easy to spot. (Which will be especially useful now that Sophie is running. Everywhere!)