diff --git a/tinycolor.js b/tinycolor.js
index 9ce79d8..2594fdd 100644
--- a/tinycolor.js
+++ b/tinycolor.js
@@ -55,6 +55,117 @@ tinycolor.prototype = {
     isLight: function() {
         return !this.isDark();
     },
+    /**
+     * The color with less brightness value is considered as Darker.
+     * @param {tinycolor} secondColor 
+     */
+    isDarker: function (secondColor) {
+        return this.getBrightness() < secondColor.getBrightness();
+    },
+    /**
+     * Return the opposite value of isDarker().
+     * @param {tinycolor} secondColor 
+     */
+    isLighter: function (secondColor) {
+        return !this.isDarker(secondColor);
+    },
+    isWarm: function () {
+        return this._r > this._b;
+    },
+    isCool: function () {
+        return !this.isWarm();
+    },
+    /**
+     * Returns true if the color is warmer i.e. have more red value. 
+     * If both colors have the same red value the one with less green and blue values is considered warmer.
+     * @param {tinycolor} secondColor 
+     */
+    isWarmer: function (secondColor) {
+        if (this._r > secondColor._r)
+            return true;
+        if (this._r == secondColor._r) {
+            return (this._b + this._g) < (secondColor._b + secondColor._g);
+        }
+        return false;
+    },
+    /**
+     * Return the opposite value of isWarmer().
+     * @param {tinycolor} secondColor 
+     */
+    isCooler: function (secondColor) {
+        return !this.isWarmer(secondColor);
+    },
+    /**
+     * Returns true if colors are harmonious with the selected harmony.
+     * 
+     * @param {String} harmony 
+     * Should be a value from ['complement', 'analogous', 'monochromatic', 'splitcomplement', 'triad', 'tetrad'].
+     * @param {tinycolor[]} otherColors
+     * List of the colors to be checked.
+     * you have to pass 
+     * 1 color for 'complement', 'monochromatic',
+     * 2 colors for 'analogous', 'splitcomplement', 'triad', and
+     * 3 colors for 'tetrad'.
+     * @src https://www.sessions.edu/color-calculator/
+     */
+    isHarmonious: function (harmony, otherColors) {
+        var len = otherColors.length;
+        var result = false;
+        switch (harmony) {
+            case 'complement': {
+                var compColor = this.complement();
+                restult = compColor.toRgbString() == otherColors[0].toRgbString();
+            }
+            break;
+            case 'analogous': {
+                var anaList = this.analogous();
+                for (var aIndex = 0; aIndex < anaList.length; aIndex++) {
+                    if (!(otherColors.includes(anaList[aIndex]))) {
+                        result = false;
+                    }
+                }
+                result = true;
+            }
+            break;
+            case 'monochromatic': {
+                var monoList = this.monochromatic();
+                for (var mIndex = 0; mIndex < monoList.length; mIndex++) {
+                    if (!(otherColors.includes(monoList[mIndex])))
+                        result = false;
+                }
+                result = true;
+            }
+            break;
+            case 'splitcomplement': {
+                var splitList = this.splitcomplement();
+                for (var sIndex = 0; sIndex < splitList.length; sIndex++) {
+                    if (!(otherColors.includes(splitList[sIndex])))
+                        result = false;
+                }
+                result = true;   
+            }
+            break;
+            case 'triad': {
+                var triList = this.triad();
+                for (var tIndex = 0; tIndex < triList.length; tIndex++) {
+                    if (!(otherColors.includes(triList[tIndex])))
+                        result = false;
+                }
+                result = true;
+                
+            }
+            break;
+            case 'tetrad': {
+                var tetList = this.tetrad();
+                for (var tetIndex = 0; tetIndex < tetList.length; tetIndex++) {
+                    if (!(otherColors.includes(tetList[tetIndex])))
+                        result = false;
+                }
+                result = true;
+            }
+        }
+        return result;
+    },
     isValid: function() {
         return this._ok;
     },