It is going to sound strange but here is the question In the toilet there are these blue things that clean your bathroom with every flush by adding bleach hence it colors the water blue every time you flush are they allowed on Shabbos, On the same topic if I have a nose bleed and use a tissue is that Tzoveah?
I am going to deal with the bleeding first.
Is where the whole complicated matter gets started. Well actually it gets started in the same place in the Tur, where the Beit Yosef cites the Yeraim saying that when eating berries etc. and one’s hands are dripping with colored fruit, care should be taken not to touch clothes or napkins, because of coloring. Even though it is mekalkel, it is ossur mid’rabanan. He adds that it is prohibited to place a cloth etc. on a bleeding wound because of. The Bais Yosef in siman 328:38 complements this saying that one should wash the wound and then place the cloth. The subsequent coloring of the cloth is through a g’rama, because the wound had no blood when the cloth was placed.
The Darchei Moshe in siman 320:2 says that the Agor(one of the Rishonim) holds that one may bandage a wound with a cloth or wipe one’s dirty hands on a cloth because it is called dirtying and has nothing to do with coloring.
The Magen Avraham 320:24 rules in accordance the Beit Yosef, against the Darchei Moshe. The M”A also says that wiping blood with a red cloth is worse than wiping with a white cloth. This can either be because the newly applied red color strengthens the old color or because it is not possible to say that it is dirtying when it is the same color. The M"B rules the same way.
From there the conversation heads in the direction of menstruation and the sheva nekiim: The Shulchan Aruch 303:15 says that a woman may wear a cloth used for absorbing menstrual bleeding in a reshut harabim, and the issue of coloring the cloth never arose.
The Shulchan Aruch HaRav learned from here that a cloth designated for that particular use is not prone to coloring, because one does not care for its coloring. Only a regular cloth, which I understand to mean that sometimes one would dye it intentionally, is prone to the problem of.
Rav Shlomo Zalman Auerbach says(as quoted in Shemirat Shabbat Kehilchta 14 footnote 62) that dyeing the cloth with blood is not coloring, because one is merely using the cloth instead of a spoon and not in order to color the cloth.
One should l’chatchila wash a wound before applying a cloth. The Shmiras Shabbat 35:18 says that bandages, plasters, gauze and everything set aside specifically for this purpose may be applied without prior washing the wound. This is based on the Shulchan Aruch HaRav mentioned previously.
Rav Auerbach also permits wiping with a tissue or disposable napkin because one does not care for its coloring since it is being disposed of.(Shmirat Shabbat 14:19)
Now as far as the toilet Coloring water for a decorative purpose is strictly forbidden even though water in itself is “food”, M”B 56.
It is much more tricky The reasons permitting it are a) the intention is to disinfect and ‘by the way’ the water gets colored. B) It is done by way of Grama- an indirect action, because flushing the water ‘causes’ the color to be flushed from the small container and color the water.
The reasons prohibiting it are A) the intention is to color the water as well, not only to disinfect; otherwise they could manufacture colorless disinfectant. B) The first rush of water is called your action and not.
It is a mahloket poskim. Where some permit and some forbid. Personally I am machmir and remove it before Shabbos, since Rav Shlomo Zalman forbade it(Shmirat Shabbat 23:14). Removing it on Shabbat involves muktze and one should do so with one’s foot. When confronted with this apparatus in someone else’s house, I suggest lifting it a bit with one’s foot and flushing (requires a bit of deftness). If impossible, I think one should flush (maybe using an elbow?) and rely on the lenient opinions because of Kavod L'Briut.