Having a hard time with colors

My solution to this problem is getting a color palette from adobe website:

https://color.adobe.com/explore

Here you can find numerous color palettes from designers etc, and you can follow the trends

https://color.adobe.com/trends

I hope that you will find it useful as well :)

You can start with this blog and then understand a little bit better how colors work abd then use palette and learn how to derive colors because usually you have 2-3 mains colors but with all variation almost 20.

Normally you decide on your branding and chose 2-3 colors as your color palette. Then all your elements should fit within this palette. As how to choose twose 2-3 colors, it's usually a matter of preferences and what suits your business better. Just make sure the contrast is high enough and the colors are not really ugly next to each other (do try complementary colors for example).

Quick and cheap (free): if you don't care about branding a lot, just use an existing UI Kit, Framework or whatever, there's many. People usually go with Bootstrap.

There's a really nice series of tweets by Steve Schoger that provide tips for color selection, contrast, etc. He also has some videos on YouTube you should definitely check.

There's a lot of extra info here: https://www.indiehackers.com/forum/resources-to-help-you-improve-your-ui-design-134dbd3367

While there is a science to choosing complimentary color palettes, there is an art (or at least some mix of psychology and culture) to picking your dominant colors to match the brand goals of your company. Building something that minimizes financial risks for your client base? Consider a fairly dark blue as a starting point. Building something that helps businesses grow? Think verdant green or sunny orange. Building something that makes motorbikes go 10% faster and your customer base is 98% thrill-seeking macho men? Think charcoal with a secondary dark red. Your dominant color sends a branding message.
Once you work out your dominant color brand psychology, you can use the palette tools others have suggested to explore secondary/complimentary colors (and typography). Consider hiring a designer or at least inviting your most brand-savvy and good-taste friend over to work through it.