To begin with, the colour scheme of greens, blues and purples reflect, not just a love of Balmoral as has been widely reported, but also Eugenie's and also her Mother's Coats of Arms which carry a thistle or thistle heads. This colour scheme was reflected especially in the costumes for the bridesmaids and pageboys.
The Thistle is one of the main symbols featured on the Grant of Arms to Sarah, Duchess of York's late father. (Please see the Blog on Sarah, Duchess of York.) A trend started with the Dukes of Cambridge and Sussex, Eugenie's older cousins, now sees their Labels of Difference reflecting the maternal Arms of Members of the Royal Family. In William and Harry's cases it was the Scallop Shell of the Spencers. The other symbol on the Duchess of York's Shield is a Bee which features on Eugenie's elder sister Beatrice's Label, which is also, in turn, an example of heraldic punning, reflecting Beatrice's nickname. (You may have noticed that Beatrice wore a diamond brooch in the shape of a Bee at her sister's wedding.)
The Bride's bouquet and the Groom's buttonhole also had heraldic significance as the main flowers were white roses and, again, thistles. The white Rose is the symbol of York/Yorkshire and therefore also the Badge of the Duke of York, in other words Eugenie's father, as shown below.