There are a lot out there, but here are some of my favorite generators. Most listed allow you to enter in your own color like you specified.

- [ColorKitty](https://colorkitty.com/) - Palette from image
- [Cohesive Colors](http://javierbyte.github.io/cohesive-colors/) - New palette formed by old palette + color overlay
- [Colour Lovers](http://www.colourlovers.com/) - Palettes based on color or combination
- [Handy Colors](https://yoksel.github.io/handy-colors/) - Palettes from named colors (handy for testing) and some pre-made palettes
- [Picular](https://picular.co/) - colors from search terms
- [ColorBox](https://www.colorbox.io/)- Generator by Lyft
- [Data Color Picker](https://learnui.design/tools/data-color-picker.html) - Generator ("specifically for data visualization")
- [Colormind](http://colormind.io/bootstrap/) - Generator that uses UI to show the colors
- [Couleur](https://couleur.io/) - Generator
- [Palx](https://palx.jxnblk.com/) - Generator ("specifically for UI")
- [Geenes](https://geenes.app/) - Generator
- [Color by HailPixel](http://color.hailpixel.com/) - Generator
- [ColourCo.de](http://colourco.de/) - Generator
- [Adobe Color CC](https://color.adobe.com/create/color-wheel/) - Generator
- [Coolors](http://coolors.co/) - Generator
- [Palette App](https://palettte.app/) - Generator
- [Color Supply](http://colorsupplyyy.com/app/) - Generator of 2-color palettes
- [Poolors](https://poolors.com/) - Color combos least used by designers.

There are also some sites that give you pre-made palettes, including those of popular brands

- [Google's Material palette generator](https://material.io/tools/color/#!/) - Generate material color templates according to their design guidelines <sup>(well, [close](https://graphicdesign.stackexchange.com/q/94117/23061))</sup>
- [Brand Colors](http://brandcolors.net/) - Brand colors
- [Happy Hues](https://www.happyhues.co/) - Palettes that you can preview applied to a webpage
- [Colors.lol](https://colors.lol/) - Overly descriptive color palettes.
- [Culrs](https://culrs.com/#/) - Picked palettes based on color type
- [Poke Palettes](http://pokepalettes.com/) - Palettes based on Pokemon
- [Color Leap](https://colorleap.app) - Palettes based on time periods
- [Found Color](https://foundcolor.co/) - Palettes from curated photos
- [The Day's Color](http://www.thedayscolor.com/#info) - New palette daily
- [Minimalist Color Palettes](https://www.behance.net/gallery/32154055/Minimalist-Color-Palettes-2015) - A great selection of hand picked palettes
- [Website color schemes](https://designschool.canva.com/blog/website-color-schemes/) - Color schemes with adjective descriptions
- [Colors](https://klart.co/colors) - computer generated palettes
- [Color Hunt](http://www.colorhunt.co/) - Mutliple palettes daily
- [Conic.css](https://conic.style/) - Conic gradient pre-made palettes.

There are also some sites that offer gradient combinations which you can get the color codes from:

- [CSSGradient](https://cssgradient.io/) - gradient generator
- [uiGradients](https://uigradients.com/) - probably my favorite gradient site
- [HD Gradients](https://gradient.style/)
- [Hypercolor](https://hypercolor.dev/#gradients)
- [Grabient](https://www.grabient.com/)
- [Webgradients](https://webgradients.com/)
- [Eggradients](https://www.eggradients.com/)
- [Color Designer](https://colordesigner.io/gradient-generator)
- [Gradient Magic](https://www.gradientmagic.com/)

Or you could let AI choose some colors for you using [AI Color Wheel](http://brandmark.io/color-wheel/).

___

I also like to look at the chart below (pulled [from here](https://www.lifewire.com/contrasting-foreground-background-colors-4061363) when considering which colors to mix (usually on top of the gradients above) for best contrast:

[![colors contrasted with each other chart][1]][1]


  [1]: https://i.sstatic.net/DprtN.png