When dressing up a vest, I would apply the same basic principles that I would use to dress up a jacket. Between the shirt,tie and vest there should be at least one item that has a pattern in it. If between the three there are no patterns, it looks boring. If all three have patterns it looks too busy. When choosing a tie, my preference is always a contrasting colour. Then I look for colours in the patterns of the tie that are the same colours as the jacket and shirt. If I cannot find one that matches both, then I choose a colour that matches the jacket.
If you do go with a red coloured tie, then go with a white boutonnière. If you want to go with the grey or any other coloured tie, go with the red boutonnière.
You can also do an internet search on "dressing up a vest for men". There you can find many examples of vest, shirt, tie combos.