My niece has asked that I try to do a similar cake for her wedding. I thought this would be easy, but cannot get the colours to blend properly and I ended up with a rough mess. Can anyone tell me how I get the smooth strokes or texture lines and nicely blended colours with this buttercream cake? 

I used real butter buttercream and spatulas. 

Thank you

Can you link us to a picture of what you want?   There is no way to post it here but if it’s anywhere on the web you can post a link so we can see it 

Yes, no picture so impossible to help without a picture. Try to copy and paste in your post here.