Puzzle #96: Marbles That You Have Not Lost

TRU students (and students at other universities) will be writing final exams soon. Best wishes!

You have some marbles. Each is one of six colours: red, orange, yellow, green, blue, and violet. Given the clues following, how many are there of each colour?

1) There are more orange marbles than blue ones; there are fewer violet marbles than red ones.
2) The number of orange marbles and green marbles combined is equal to the number of yellow marbles and violet marbles combined.
3) Each colour has a different number of marbles, and these numbers are all in the range of two to nine.
4) There are three times as many violet marbles as yellow marbles.
5) There are 28 marbles.

Submit your answer to Gene Wirchenko <genew@telus.net>. Your answer should be in the form of a proof. That means to show how your answer must be correct. The deadline is Wednesday, April 8, 2015 at noon Pacific Time. I will post the answer shortly after.