You can consider matching with the same color system. For example, the coat is dark blue, that is, a simple light blue shirt and the like, with the same color but contrasting shades. Of course, if you want to add patterns, you can consider a blue and white plaid shirt instead of the old white T (so you can have the white you want).

If we consider the collocation of adjacent colors, the ones close to blue are green and purple. But these are still blue. Sky blue and lavender purple are a perfect match; Soft light blue and light green are also sweet and beautiful. . .

Considering the contrast between cool and warm colors, it is important to have a bright effect. For example, use red, yellow, orange and brown. Brown is compatible with different degrees of blue. Wine red and dark blue are also good; Pink orange and pink blue are also nice. Golden yellow and bright blue are also very eye-catching (like the oil paintings of crows in Van Gogh's wheat fields). This technique is very common in accessories. For example, you can consider using these colors for your scarf. Especially when your overall dress is dark and harmonious, a scarf with contrasting colors can make you light up immediately.

Finally, it is safer to match with white, black and gray. (You can also consider using some yellow and white). The brighter the blue is, the easier it is to match black and white. For example, you said white T, but I still feel lazy. If it's gray-blue, it's more expensive to use gray.