[orx-palette] Add nextColor(2) for easy palette permutations (#140)

orx-palette/src/main/kotlin/PaletteStudio.kt

@@ -51,6 +51,14 @@ class PaletteStudio(
     var randomizeKey = 'k'
 
     private var paletteIndex: Int = 0
+    var nextColorIndex: Int = 0
+    get() {
+        return field++ % colors.size
+    }
+    var nextColor2Index: Int = 0
+    get() {
+        return field++ % colors2.size
+    }
 
     enum class SortBy {
         NO_SORTING, DARKEST, BRIGHTEST
@@ -196,6 +204,12 @@ class PaletteStudio(
         return paletteIndex
     }
 
+    val nextColor: ColorRGBa
+    get() = colors[nextColorIndex]
+
+    val nextColor2: ColorRGBa
+    get() = colors2[nextColor2Index]
+
     fun randomize() {
         palette = assemblePalette(colors.shuffled())
     }