Choosing a window covering for a bathroom window can be a tough choice to make, most of the time you will already have some kind of frosted glass to protect you from people looking in, so the window covering is purely aesthetic.
Having a net or lightweight curtain in your bathroom is certainly a valid option, the only problem is that they absorb water, and then take ages to dry off, which could damage themin the long run.
In terms of blinds, it would be wise to choose a waterproof product for your bathroom. One great option is aluminium venetian blinds which are probably the most waterproof blinds available, although you may want to consider vertical or roller blinds which use a waterproof fabric.
If your fear is choice of colour then I can dispell that right now, their are literally hundreds of colours available in aluminium bathroom blinds. To further the choice even more you can choose between 25mm, 35mm and 50mm slat widths depending on the style you are going for.
If you were not to use a water proof fabric overtime the fabric could deterioriate or even become moldy, which is something you definitely don’t want in your bathroom.