Ryna's answer suggests splitting up over more,simpler pages, but it sounds like your clients want simultaneous access to all of it. So let's see how far we get without changing the layout.
The problem here isn't so much the amount of data, but the visuals. You've got a gradient background, an outline, the same background, another outline, and then a white background. Plus there's a pretty strong color contrast between all those elements. All in all, quite a lot of complexity.
You can either have complex data, or complex visuals.
If you have both it gets too busy. (If you have neither, it could be boring, but that's less bad)
In this case you have fairly complex data, so your presentation should be rather simple. Try working more from gestalt theory, flat design, and try to minimize the amount of objects and visual ridges:
The layout is nearly identical, I only aligned the textboxes a bit more according to a grid. But I removed a lot of visual complexity:
- no more outlines on textboxes and buttons
- no more gradients
- unified the color palette
- made secondary info more subtle
- made icons more symmetrical and softened the shading
- slightly tweaked dropdown box
By far the important change out of all of these is removing textbox outlines:
Notice how much more unified the data fields are after just one tweak? This is because the contrast between the dark blue outlines and the white background is almost as strong as the black-on-white text would be. And outlines have no need to be that noticeable, they're just supposed to be a slight bump to keep you looking in the right area.
Visual hierarchy should match information hierarchy
There are two basic kinds of hierarchy; priority, and similarity. Priority is about which things should be seen first, similarity is about which things go together.
Priority is more of a small-scale thing, while similarity is about larger blocks of content. But both use the same basic toolset revolved around contrast: color contrast, text versus image, animated or static, different size, and so on.
The most important here is the content of the textfields. This is the data stored in the database, the information about your client. It's what you come to this page for. We want the highest contrast for this. Black on white is a good option here.
Sometimes you can intuitively see what's what ; James van Borgenstein, 12-06-1921. But sometimes you can't; is 555-6449134 a fax number or phone number? Luckily we can show labels. They should be noticeable, but not quite as much as customer info. Luckily we've already got a light-blue background, which contrasts well with black, but not as strongly as a white background does.
We also have dropdown menus, which are on a white background. To get lower contrast than the text, don't make these black, but dark blue.
So we end up having a light and a dark blue. Which can be used together to create a tertiary layer of importance. I used it to soften the note since it was already in brackets, but you could also choose to make the labels dark blue and just "primary address" as black.
The icons are also a secondary element, but not as straightforward to explain. They're thicker objects than the label text, and they have stronger contrast too. (Perhaps I should have toned them down slightly?) But they are grouped together, similarly to how the textfields and labels are grouped, which brings us to...
All of the textfields contain customer info, the labels are explanations of what each field is, and all the icons lead to different (external?) screens. We should style things so we simultaneously group similar things, and separate each group from another. We've got the same basic tools for that, we just need to look at a larger scale.
The most important group is customer information. They're already together in your layout, so that's good. When we remove the outlines from them (and you squint a bit) they form a pretty solid, and highly noticeable block against the lightblue background. Light colors also seem to be closer than dark ones, as do red colors vs blue ones, so the whole textfield block seems to jump off the page.
Our secondary elements , the text and icons, are black on lightblue. So the local contrast is lower, which is a good start. But in addition they share that background color with the entire screen, which means that there's also less global contrast. Just a couple of thin black lines instead of complete color blocks means that the local contrast is diluted a bit.
Which leaves the icons. They're slightly more contrasted than the labels, but they're also smaller. And due to the location they won't be seen as related to the labels; icons and labels are divided by a large white plains.
If we were to look one step larger than this, Primary Address vs Additional info, we could separate the two by lines as you do in your original picture. But if you look at the blurry version, you can see that the light textfield block is already sort of outlined by the darker labels and icons. So if we're looking at a full page of these, you could very easily skim the white areas, and then if necessary look at the secondary information.
So here we see 3 scales of information:
- what kind of customer information (Contact, Billing, Insurance, etc)
- what sort of group (customer data, explanatory label, extra options)
- the actual information (name, phone number, etcetera.)