Here's one of my Blue exchange cards all together.
These were done extremely on the cheap - I bought some blue A5 card, painted the flower outlines, used 23ct gold leaf to gild three sections on each flower, then did the calligraphy and then painted in the colour. To get the colours I used ultramarine + zinc white gouache in three different ratios - light, medium, dark. That's my cheat's way of making sure all the colours blend ... it's all just one colour!
Things I'd change: I think I would paint the petals before doing the calligraphy next time as it looks very amateur with the colour not meeting the letters. I will also not be using that brand of cardboard again as it was bleedy to the max! And I would have worked harder for consistent coverage with that background painting - maybe I'd use acrylic or watercolour instead of gouache. Things just weren't going my way that day.
The overall effect came out OK, though. And I look at it every time as: each exchange is something new to learn