This doesn't match your wedding colors, but it truly delicious and meets your other requirements of tasty and moist.

White cake mix. Be sure to use only egg whites if the recipe doesn't call for it. Follow directions with these exceptions.

1 can of mandarin oranges. Drain well into measuring cup to use juice as part of your water. Then fill up to appropriate measure for water.

When cake mixture is completely mixed, using your mixer (kitchen aid really makes a difference!) blend in the mandarin oranges. These should be broken down and mixed well.

Bake as normal.

I prefer a 7 minute frosting to top this. (But I really love the stuff. Can eat it by the spoonful which I can't do with any other frosting... ug). The canned whipped white frosting is 7 minute frosting and is quite good. Cream cheese frosting would also work.

Just thinking, you could also do a strawberry version of this or mix strawberries and mandarins together.

Congratulations on your engagement!!!

Count it all joy :)