How to know for sure?  

You could start buy putting a line of paint on the wall to check it out. You may want to stick to neutral colors like white or off white. I would not want to keep painting over that bathroom. those two colors are not on the top of my list either.

mmmm, that's strange question - how to know in advance...When we wanted to choose a beige colour for our sitting room, we took tow or three samples of beige colour because all these beige colours looked the same...and we painted small stripes with these samples that looked really similar and guess what? they were totally different!!! One colour was little bit like lilac beige, one was warm caramel colour and one was really light beige that we chose. It can be that you like pink colour but probably you chose not right tone of pink. I should suggest to try samples if you cannot paint on wall sample colour tone then paint it on papaer and then stick that paper to the wall and try to imagine how it all could look in that specific colour Good luck!!!

photoshop ? no i find you cant tell till its too late- i painted mine deep purple once, mind you i should have known that was a bad idea

First off, bear in mind that something that looks lovely and cheery on a paint chip will intensify dramatically on four walls, or four walls and a ceiling. I imagine that is what happened with your lovely pink. Pink is better than the lilac, as lilac has too much blue or gray and will make things kind of drab and dull. Pink is a good color, and is flattering to the complexion, but I can already see that if that is your pink it is just too much. What if, instead of repainting it totally, you were to take a glaze or overcoat and sponge or texture paint over the pink. I had some bright pink in my bathroom once, and I used just a bottle of ivory craft paint and sponge painted ivory over the whole thing. It helped immensely, made the room more interesting and broke up that solid bubble gum pinkness.

If you cannot make up your mind the safest bet would be pure white colour or any very light pastel colour that of blue, pink, green or lavender - I think they look good. I have got all the three bathrooms painted in the shades I mentioned - originally they were but they seemed too bright especially when the sun shone in.all white. So if you need a bright bathroom go for the white.

Hi, MagicalBubbles. If you had a piece of fabric with the color of your paint, then you can put this up against the wall. You can compare that color to the paint color. You can see if this color will fit your wall.