Hello, everyone, I’m a new guy here!
I’m designing a site for Windows 7 now, amd i met some questions about colors.
I don’t know what is this other class of colors that look like these: #1A203C, #3F4F5F
This is the colors i used most: combine O 6 C and F, for example: #F6666F and # OO33CC
Can you tell me the difference between them?
Thanks very much
The color values are just examples of some of the 16 million possible values.
Your values are basically a sub-set known as “web safe colors”.
You might actually find a color application useful in helping you find the color you want (and shade), that way you will be given the correct hex code associated with it without having to try and guess how everything will appear. I use a paid product called ColorSchemer Studio but there’s free products out there like Color Cop or Adobe Kuler (I’ve included the links below) that will help you pick colors and will give you the right code you require for it. 
Thank you so much
I will try it