Thanks everyone.

I had wondered about the spew issue and if one twin had used/soiled all her clothes I'd have to resort to dressing 'Lexie' in 'Mae's' clothes. But I don't think that would be a huge issue, it'd only be an interim thing on a bad day ... people tell me I'll be washing non-stop anyway.

Lexie is our lively twin and Mae is our calm, chillaxed twin (or that's the plan).
So far I've sorted Lexie to have all the bold colours (hot pink, red, anything with stripes) and Mae to have the pastels (pale blue, lilac, mint green and softer prints).
I know it sounds stupidly and probably wishfully organised to have the clothes set up so rigidly. I am an OTT organised person so maybe it's just a psychological thing where I am trying to convince myself that I can have a toddler, twins and still be organised. I give my system 2 washes and it will be utter chaos and I may end up dressing the twins in my toddler's tracksuits.
Mainly trying the separate colours to stop the 'Which twin am I holding' questions. While my girls are not ID, for a while they will both just look like newborns and I can just tell the constant questions regarding 'Who is who' will drive me batty. Guess I can't help it though.

Good point about the non-removable labels, I plan to just pass on or donate all our clothes after the twins grow out of them - we have a gorgeous DD who is 2 and the twins will now complete our family. It's a shame to have non-removable labels on clothes that I plan to pass on to friends but the labels will be ironed on the inside so no one would see them when dressed on another little girl? No phone numbers, just names.
Maybe I will just iron the labels on the 'good stuff' (dressy clothes I want to keep separated for each bub) and not worry with the day to day wondersuits etc.

I must admit, I have an obscene amount of girls clothes. I had a lot from having DD - and back then everyone commented 'Gosh you have so many clothes'. I think now that perhaps subconsciously I knew I was going to have twins one day as I've really not had to buy a great deal of other clothes to accommodate for twins. It's been creepily insane as I've unpacked all of DD's baby clothes - the number of times I purchased the same top but in a pink and then a purple.
I have bought a few outfits the same but in different colours for the twins; I just hope they are in the same size at the same time.

Keep the opinions and ideas coming ...