I think your first sentence said it all - "my colleagues"! I have my own salon (for 6 years), and yes staff are colleagues, but first and foremost they are your employees, not acquaintances, and not friends. This may sound very harsh but they need to know that you are employing them, not the other way round. They are not doing you a favour by working there, you are the boss. This may sound very harsh (esp those who are self employed) but I have learnt this from (bad) experience. Staff meetings are the best way to slog it out as quite often one person doesn't do something because someone else never seems to do it so they don't feel they should do it either, if that makes sense. I have one to ones with staff if I feel things are not going right and ask them why. Then it comes to light that so and so only does whatever and therefore why should they do it. The other person may have the same feelings but with a different issue (ie one person only cleans the floor but never the wax pots but the person saying it may only clean the wax pots and not the toilet!) Never divulge what issues came from what person but bring the issue to a meeting and let the staff know exactly what is expected from them - maybe do a rota if that is necessary.
I know this may sound quite dictactorial, but since I have been doing this my staff have all been happier. They know they can approach me with any subject anonymously and I will bring it up in a meeting and it will get resolved. I have only needed to have about 3 meetings to get this sorted and it has resulted in the "lazyer" members not liking it and leaving the salon - no great loss if not a team player.
As a final word, I am now very friendly with all staff and we often go out for drinks, meals etc (not too often as I am older and cannot stay the distance!) and we have a great time.
But they need to know exactly who the boss is - for their sake as well as yours. Sometimes it's a bit like having children and making sure they know the boundaries - they will try and push the boundaries but if they know you will stick to the rules they will appreciate it in the end.
Sorry for the rant but hope it helps. Having your own salon is VERY hard - I know.