Translation:I bought many colored pencils.
Is it not accepted? That's what we've always called them. Pencil crayon is Canadian English. It originated long ago from a misunderstanding of the packaging as pencil in French is crayon, from which in turn the English word crayon is derived, now usually meaning only wax crayons AFAIK, but also pencils for colouring as in Poet Laureate John Dryden's day, say . . .
"colored pencils" is common usage in the US; I've honestly never heard/seen "coloring pencils" lol
It's always interesting going into discussions to see the many different words we use to call the same thing.
Report the question again if it continues to not be accepted. Our contributors have quite a lot of work to do right now with the new tree coming, but they'll certainly get to them eventually. Continued reports are more likely to get them seen and responded to.
I guess it makes sense as long as the colours of the pencils themselves correspond to the colours that they produce. From a grammatical point of view colouring probably makes more sense as it describes the function of the pencils whereas 'coloured' describes the pencils' appearance (which happens to correspond to the colours they produce when you draw with them). It could potentially cause ambiguity though... I mean what prevents someone from making pencils that are coloured in appearance, but produce only black colour? you'd still call them coloured pencils as that's what they are but they don't produce colours as you'd expect them to.