Being as all this may, there are colours
and there are colours...
Using oxygen bleaches on light/pastel coloured items even in hot water probably should be fine. Once you start going into more richly coloured things long as water temps are kept to warm or even cold (86F) again things should be fine, but shouldn't make a habit of it. Dark blues, blacks, browns, etc... are another matter all together.
Much depends also on what type of oxygen bleach one is using. Sodium perborate long was considered the "colour safe bleach" because it requires temps >120F and really 140F or above to really get going. Since most persons aren't going to wash colours in hot or boiling water chances of damage would be minimal. This is one of the reasons why Colorx2, Biz and the host of other early such products used SPB.
Sodium percarbonate OTOH is known as the "cold water oxygen bleach" because it can and will become active even in cold water. Therefore even routine use with some colours even in cool to warm temps can cause fading over time.
Liquid hydrogen peroxide like sodium perborate requires hot to boiling water to become really effective. European laundries long have used pure highly concentrated LHP as a liquid bleach along with boil wash temps. Many prefer liquid hydrogen peroxide because it is near neutral since it is not based on alkaline substances (sodium carbonate/washing soda or borax) like dry oxygen bleaches. This means among other things you can use liquid hydrogen peroxide on protein fabrics such as silk or wool if you know what you are doing. Also since it is pure less rinsing is required when using liquid hydrogen peroxide. Much of the stuff simply breaks down into water when exposed to air, light and high temperatures. This is why LHP is always sold in dark bottles with warnings to keep tightly closed.
Forget the exact ratio but IIRC it is for ever ten degree increase in water temperature oxygen bleaches become twenty times stronger. Persons with knowledge of proper use can and do use oxygen bleaches on textiles ranging from fragile to deeply coloured by using their expertise to control the bleaching action strength. That is if you want to remove a tea stain from a blue shirt, it probably can be done and still keep the color.
Liquid oxygen bleaches are still sold here in the USA. Don't know about "Snowy", but Vivid and Colorx 2 are both still around. However even going back to the 1980's when Consumer Reports tested both powder and liquid oxygen bleaches the liquids came in dead last for stain removal, whitening, and so forth. Colorx 2 powder was first, then BIZ.
Finally on both sides of the pond oxygen bleach powders (sodium percarbonate and sodium perborate) have long been combined with activators. Tide w Bleach, Oxydol, Persil, Ariel, etc.... all have such systems. Indeed P&G and Henkel have scores of patents on such systems and keep them closely guarded.
Because these activated bleaches will work in cooler wash temperatures (mainly for sodium perborate, but also sodium percarbonate), consumers are often advised to restrict their use on colors. Both Persil and TWB are known to fade some coloured textiles with routine use. Hence the need for "color" detergents that do not contain oxygen bleach activated or otherwise. To save having to stock two sorts of detergents many simply purchase a color version and add oxygen bleach when needed.
