CSS shows overwritten styles for a split second - angularjs

Question

Currently, I am using a directive from a third-party library for a UI toggle button. I changed the background color and left/right positions of the toggle button a bit to meet my business specifications. E.g. the out-of-the-box style came as light green for true, light red for false; I changed this to a darker green for true, and a light grey for false. I also moved the toggle positionally a bit to the left. All of this works fine.
The one issue I'm experiencing is that for a split millisecond when the page with the toggle button renders, I see the old style quickly change from what came out-of-the-box, to my updated style. There aren't any other glitches in style after this fact, just the initial loading shows some quick shifting around on the element. This isn't a huge issue but I can't seem to pinpoint the issue or know why it is happening. Any thoughts? Something in an issue for CSS hierarchy perhaps?
Notes relevant to the issue:
I used the inspector to find the classes I needed to override, since the directive itself just uses an nz-toggle tag.
I am using !important to override. I've read that this is bad practice in itself but it is being used across the entire project and has been established as "our standard" of overriding styles
Here's an example of one rule from my CSS file compared to what comes out of the box:
.nz-toggle-wrap.true {
background-color: #089900 !important;
right: -16px !important;
width: 50px !important;
height: 28px !important;
}
vs.
.nz-toggle-wrap.true {background-color: #60bd68;}
Any thoughts?

Answer 1

This happens because your "new" CSS loads after the "old" CSS.
Of course that should be true anyway, because you want to override the old style, but it seems that the old and new code are too far away from each other hence you manage to see it change.
To solve this you have to move the new style "closer" to the old style.
The way to do it depends on your project architecture and your build process.
Another option is that the class "true" is added only after page load, and so only then your new style kicks in.

Answer 2

If you are loading this "third party library" locally, you might have to directly edit the CSS files of the plug-in.
With the plug-in you linked, maybe you need to edit this file directly to prevent the "flicker", which is caused by the styles loading in sequence:
https://github.com/tannerlinsley/nz-toggle/blob/master/src/nz-toggle.styl