This has been mentioned a couple of times recently. It depends on the brand of powder you are using - some of the clears are not crystal clear and could cause the finished effect to be cloudy. Equally as powders have improved and developed, some of the pinks are too pink for mixing with some of the paler colours.
My advice would be to use your best judgement depending on your brand - I use Creative and know that the clear is crystal so I would use clear on all of the pale colours. As most people would carry much more pink than clear, I would use the pink for the stronger colours.
I hope that helps.
