Here are some tips if you want to color a pixel drawing-

Make sure not to color everything in one color:

Above is a pixel sword in one color (Hex code - #d5e26f)

You may color a little of it with plain colors.

Color from light to dark or dark to light:

Make sure to swap the orders from time to time it will make your coloring bright!

Add some detail!:

I've added some sparks to the main part of the sword.

Make sure you darken the sparks gradually!

And that's all!