A dark blue dress reference shows a pale motif colour repeated across upper body and skirt. Narrow shoulder lines are accompanied by extra side bands around the upper arms. The skirt widens downwards. The picture shows a dress; for separate pieces, the recurring colour relationship is the useful idea. You do not need to reproduce the entire pattern or length.
Lay a patterned top beside two quieter lower pieces and look for a small colour already present in it. Try the actual garments together in the same light. If two blues nearly match but do not convince you, test a more deliberate contrast. Then decide whether the waist connection should remain clear or overlap more.
Borrow the side shoulder bands only as a separate idea if you specifically want that line. They cannot establish bodice support. A neck accessory adds another upper boundary, so compare it after the basic outfit. The pictured dress composition and construction are unverified and unnecessary for this particular colour comparison.