/* Keyword values */
background-color: red;

/* Hexadecimal value */
background-color: #bbff00;

/* Hexadecimal value with alpha channel */
background-color: #11ffee00; /* 00 - fully transparent */
background-color: #11ffeeff; /* ff - fully opaque */

/* RGB value */
background-color: rgb(255, 255, 128);

/* RGBA value or RGB with alpha channel */
background-color: rgba(117, 190, 218, 0.0); /* 0.0 - fully transparent */
background-color: rgba(117, 190, 218, 0.5); /* 0.5 - semi-transparent */
background-color: rgba(117, 190, 218, 1.0); /* 1.0 - fully opaque */
​​​​​​​
/* HSLA value */
background-color: hsla(50, 33%, 25%, 0.75);

/* Special keyword values */
background-color: currentcolor;
background-color: transparent;

/* Global values */
background-color: inherit;
background-color: initial;
background-color: unset;

<color>where 
<color> = <rgb()> | <rgba()> | <hsl()> | <hsla()> | <hex-color> | <named-color> | currentcolor | <deprecated-system-color>
where 
<rgb()> = rgb( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<rgba()> = rgba( [ [ <percentage>{3} | <number>{3} ] [ / <alpha-value> ]? ] | [ [ <percentage>#{3} | <number>#{3} ] , <alpha-value>? ] )
<hsl()> = hsl( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
<hsla()> = hsla( [ <hue> <percentage> <percentage> [ / <alpha-value> ]? ] | [ <hue>, <percentage>, <percentage>, <alpha-value>? ] )
where 
<alpha-value> = <number> | <percentage>
<hue> = <number> | <angle>

<div class="exampleone">
 Lorem ipsum dolor sit amet, consectetuer
</div>

<div class="exampletwo">
  Lorem ipsum dolor sit amet, consectetuer
</div>

<div class="examplethree">
  Lorem ipsum dolor sit amet, consectetuer
</div>

.exampleone {
  background-color: teal;
  color: white;
}

.exampletwo {
  background-color: rgb(153,102,153);
  color: rgb(255,255,204);
}

.examplethree {
  background-color: #777799;
  color: #FFFFFF;
}