Hi, am now on my final year of a BA (Hons) in Floristry Design. I have to admit my flower arranging in oasis skills are still a bit lacking on the traditional style arrangements, but it does come to you eventually!! I agree with Snowdrop though, contrasting colours will help you visualise the shape. I have found tho some colours for me are easier to work with than others. Although did find white and lime green quite easy to work with and keeps in with colour balance. Its all down to personal preference really.
DOn't worry too much, keep going am sure you will be fine!
