Is there is any simple way to learn color code values in hexa form in html...?

Answer 1

Yes, RGB stands for Red/Green/Blue.
So every hexa represents those colors in the 0..255 range (represented hexadecimally).
FF00FF is Red: 255 (FF), Green: 0 (00), Blue: 255 (FF). So?
Red maxed out, Green none and Blue maxed out. Effect? Magenta!

Answer 2

Color code in hexa form cannot be learned, but only understood...

You make hexadecimal colors as a painter mix color, but with complementary colors to primary colors:
A painter use subtractive colors system with cyan, magenta, yellow ( and black ), screen use additive with red, green and blue.
On screen, no color is black, while on paper no color is white.

http://www.worqx.com/color/color_systems.htm

An hexaecimal color is composed by three digits ( from 0 to 9 and a to f -- 10 to 15 decimal ) pair ( each count from 00 to ff -- 0 to 255 decimal ).
Full ( ff ) red and full green make yellow, full green and full blue make cyan, full red and full blue make magenta, full red, green and blue make white.
You mix different levels of red, green and blue to compose a color...

If you're more comfortable with decimal, you can use css rgb() notation.
If you need transparency level, you can add an 'alpha channel' to define opacity of your color by appending one more hexadecimal pair, or use rgba() notation ( then, opacity is the 4th parameter, and unlike colors levels expected are integer from 0 to 255, opacity is expected to be float from 0 to 1 ). Standard tends to have rgb() notation implemented as rgba ( meaning support a 4th opacity parameter ).
Anyway, you could prefer HSL ( Hue Saturation Luminosity ) collor system also provided by css by using hsl() or hsla() ( same as rgb/rgba for standard implementation, first parameter is bounded from 0 to 359 -- but is circular, meaning than 360 is equivalent to 0 -- and second and third are from 0 to 100 ).

Answer 3

Simple way? Download Web Matrix 3 and use that to do your HTML coding. It has a HEX color picker built into the text editor itself, so you never have to look it up online or memorize it, you just pick your color and you go. Also, when I say it's built in, it's built into the prediction system itself. So for example, if I start to type my code, it'll pop up and let me pick as I'm typing that particular command - very easy to use.