diff --git a/CHANGELOG.md b/CHANGELOG.md
index df5654e..0f20871 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,8 +5,14 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Added
+- `is_valid_color` function
+- `color_complement` function
+- `select_color` function
 ### Changed
 - Random mode modified
+- Complementary color support for `color` and `bgcolor` parameters
+- `filter_color` function modified
 ## [0.7] - 2022-05-04
 ### Added
 - `fill_data` function
diff --git a/README.md b/README.md
index 78a6ac4..24f13f7 100644
--- a/README.md
+++ b/README.md
@@ -175,10 +175,11 @@ Samila is a generative art generator written in Python, Samila let's you create
 * Supported colors are available in `VALID_COLORS` list
 * `color` and `bgcolor` parameters supported formats:
 
-    1. Color name (example: `yellow`)
-    2. RGB/RGBA (example: `(0.1,0.1,0.1)`, `(0.1,0.1,0.1,0.1)`)
-    3. Hex (example: `#eeefff`)
-    4. Random (example: `random`)
+    1. Color name (example: `color="yellow"`)
+    2. RGB/RGBA (example: `color=(0.1,0.1,0.1)`, `color=(0.1,0.1,0.1,0.1)`)
+    3. Hex (example: `color="#eeefff"`)
+    4. Random (example: `color="random"`)
+    5. Complement (example: `color="complement", bgcolor="blue"`)
 
 ### Regeneration
 ```pycon
diff --git a/examples/demo.ipynb b/examples/demo.ipynb
index 9ab48e4..2dc335a 100644
--- a/examples/demo.ipynb
+++ b/examples/demo.ipynb
@@ -157,10 +157,11 @@
    "source": [
     "* `color` and `bgcolor` parameters supported formats:\n",
     "\n",
-    "    1. Color name (example: `yellow`)\n",
-    "    2. RGB/RGBA (example: `(0.1,0.1,0.1)`, `(0.1,0.1,0.1,0.1)`)\n",
-    "    3. Hex (example: `#eeefff`)\n",
-    "    4. Random (example: `random`)"
+    "    1. Color name (example: `color=\"yellow\"`)\n",
+    "    2. RGB/RGBA (example: `color=(0.1,0.1,0.1)`, `color=(0.1,0.1,0.1,0.1)`)\n",
+    "    3. Hex (example: `color=\"#eeefff\"`)\n",
+    "    4. Random (example: `color=\"random\"`)\n",
+    "    5. Complement (example: `color=\"complement\", bgcolor=\"blue\"`)"
    ]
   },
   {
diff --git a/samila/functions.py b/samila/functions.py
index c4ef5cc..64ac7be 100644
--- a/samila/functions.py
+++ b/samila/functions.py
@@ -95,17 +95,70 @@ def distance_calc(s1, s2):
     return distances[-1]
 
 
-def filter_color(color):
+def is_valid_color(color):
     """
-    Filter given color and return it.
+    Check that input color format is valid or not.
 
     :param color: given color
-    :type color: str or tuple
-    :return: filtered version of color
+    :type color: any format
+    :return: result as bool
+    """
+    try:
+        _ = matplotlib.colors.to_hex(color)
+        return True
+    except ValueError:
+        return False
+
+
+def color_complement(color):
+    """
+    Calculate complement color.
+
+    :param color: given color (hex format)
+    :type color: str
+    :return: complement color (hex format) as str
+    """
+    color = color[1:]
+    color = int(color, 16)
+    comp_color = 0xFFFFFF ^ color
+    comp_color = "#%06X" % comp_color
+    return comp_color
+
+
+def filter_color(color, bgcolor):
+    """
+    Filter given color and bgcolor.
+
+    :param color: given color
+    :type color: any format
+    :param bgcolor: given background color
+    :type bgcolor: any format
+    :return: filtered version of color and bgcolor
+    """
+    color = select_color(color)
+    bgcolor = select_color(bgcolor)
+    if color == "COMPLEMENT" and bgcolor == "COMPLEMENT":
+        return None, None
+    if color == "COMPLEMENT":
+        bgcolor = matplotlib.colors.to_hex(bgcolor)
+        color = color_complement(bgcolor)
+    if bgcolor == "COMPLEMENT":
+        color = matplotlib.colors.to_hex(color)
+        bgcolor = color_complement(color)
+    return color, bgcolor
+
+
+def select_color(color):
+    """
+    Select color and return it.
+
+    :param color: given color
+    :type color: any format
+    :return: color
     """
-    if isinstance(color, tuple):
-        return color
     if isinstance(color, str):
+        if color.upper() == "COMPLEMENT":
+            return "COMPLEMENT"
         if color.upper() == "RANDOM":
             return random_hex_color_gen()
         if re.match(HEX_COLOR_PATTERN, color):
@@ -114,6 +167,8 @@ def filter_color(color):
                                  VALID_COLORS))
         min_distance = min(distance_list)
         return VALID_COLORS[distance_list.index(min_distance)]
+    if is_valid_color(color):
+        return color
     return None
 
 
@@ -196,7 +251,7 @@ def plot_params_filter(
         raise samilaPlotError(PLOT_DATA_ERROR.format(1))
     if g.data2 is None:
         raise samilaPlotError(PLOT_DATA_ERROR.format(2))
-    color, bgcolor = map(filter_color, [color, bgcolor])
+    color, bgcolor = filter_color(color, bgcolor)
     projection = filter_projection(projection)
     alpha = filter_float(alpha)
     linewidth = filter_float(linewidth)
diff --git a/test/function_test.py b/test/function_test.py
index 48ba874..1e27538 100644
--- a/test/function_test.py
+++ b/test/function_test.py
@@ -2,6 +2,36 @@
 """
 >>> import random
 >>> from samila.functions import *
+>>> is_valid_color("blue")
+True
+>>> is_valid_color((0,0,0))
+True
+>>> is_valid_color((0.1,0.1,0,1))
+True
+>>> is_valid_color([1,1,1,1])
+True
+>>> is_valid_color([1,1,1,1,1,1])
+False
+>>> is_valid_color("nothing")
+False
+>>> is_valid_color("#FFFAAF")
+True
+>>> color_complement("#FFFFFF")
+'#000000'
+>>> color_complement("#FFAFBF")
+'#005040'
+>>> color_complement("#000000")
+'#FFFFFF'
+>>> select_color("blue")
+'blue'
+>>> select_color("#FFFFFA")
+'#FFFFFA'
+>>> select_color((0.1,0.1,0.1))
+(0.1, 0.1, 0.1)
+>>> select_color(2)
+>>> select_color(None)
+>>> select_color("complement")
+'COMPLEMENT'
 >>> s = list(float_range(1,1.5,0.1))
 >>> s
 [1.0, 1.1, 1.2000000000000002, 1.3000000000000003, 1.4000000000000004]
@@ -13,16 +43,16 @@ False
 False
 >>> is_same_data(s,[])
 False
->>> filter_color("yellow")
-'yellow'
->>> filter_color((0.2,0.3,0.4))
-(0.2, 0.3, 0.4)
->>> filter_color("#FFFFFF")
-'#FFFFFF'
+>>> filter_color("yellow", "blue")
+('yellow', 'blue')
+>>> filter_color((0.2,0.3,0.4), (0.2,0.3,0.4,1))
+((0.2, 0.3, 0.4), (0.2, 0.3, 0.4, 1))
+>>> filter_color("#FFFFFF", "#ffffe1")
+('#FFFFFF', '#ffffe1')
 >>> random.seed(2)
->>> color1 = filter_color("random")
+>>> color1, bgcolor1 = filter_color("random", "random")
 >>> random.seed(3)
->>> color2 = filter_color("RANDOM")
+>>> color2, bgcolor2 = filter_color("RANDOM", "RANDOM")
 >>> color1 == color2
 False
 >>> random.seed(2)
@@ -35,8 +65,10 @@ False
 7
 >>> len(color2)
 7
->>> filter_color(2)
->>> filter_color(4)
+>>> filter_color(2,2)
+(None, None)
+>>> filter_color(4,3)
+(None, None)
 >>> filter_size(2)
 >>> filter_size((2, 'test'))
 >>> filter_size((2, 3.5))
diff --git a/test/overall_test.py b/test/overall_test.py
index 1da3fc9..937c81e 100644
--- a/test/overall_test.py
+++ b/test/overall_test.py
@@ -73,6 +73,21 @@ True
 >>> g.plot(projection=Projection.POLAR, color=(.1, .2, .8))
 >>> g.color
 (0.1, 0.2, 0.8)
+>>> g.plot(projection=Projection.POLAR, color="#FFFFF1", bgcolor="complement")
+>>> g.color
+'#fffff1'
+>>> g.bgcolor
+'#00000E'
+>>> g.plot(projection=Projection.POLAR, color="complement", bgcolor="#AAAAAA")
+>>> g.color
+'#555555'
+>>> g.bgcolor
+'#aaaaaa'
+>>> g.plot(projection=Projection.POLAR, color="complement", bgcolor="complement")
+>>> g.color
+'#555555'
+>>> g.bgcolor
+'#aaaaaa'
 >>> g.plot(bgcolor=(.1, .2, .8), spot_size=0.1)
 >>> g.plot(size=(20, 20))
 >>> g.size