Strange coolant issue

[Simon PMB]

I have a very strange issue with the coolant on my XC90 (2007 3.2 petrol) which has suddenly changed from the normal blue/green colour to clear!

I last looked under the bonnet about 2 months ago and the coolant then was the correct colour, but when I went to check the oil etc today it has changed to a virtually clear colour, although it still smells and feels like normal coolant.

The car continues to drive great, with no overheating signs even in the extreme heat we have had this week and there are no warning messages displayed. The coolant level hasn't dropped or risen at all and the level / quality of the oil also look fine, with nothing untoward in the oil filler cap.

The car has a full main dealer / specialist service history and has always had the correct Volvo coolant. At the last specialist service in November the quality / freezing point of the coolant was checked and it was fine, not requiring replacement (although it has been in for a few years now and I was probably going to have it changed anyway at the next service).

Does anyone have any ideas why this has happened and could it be linked to the very hot weather we have been having?

Also does this mean the effectiveness of the coolant has now been compromised and should I therefore have the coolant changed asap?

Many thanks