Color ArrayPlot with custom colortable ~ ColorData or ColorRules

Question

I have a map what I would like color according to predefined RGB colors. So first I make an array of the ImageData:

Download the attached data source here: map, colors

input = Import[
  "d:\\bitbucket\\diversity\\data\\nlcd_200x200.tif", {"GeoTIFF", 
   "Image"}] 

a = ImageData[input]*255;

Then I load the colors from a CSV:

Colors = ReadList[
  "d:\\bitbucket\\diversity\\data\\nlcd\\nlcd-colors.csv", {Word, 
   RGBColor[Word, Word, Word]}, WordSeparators -> {"\t", " ", ","}]

Then I try to use the colors to make a colorful map (it's bad...):

ArrayPlot[a, ColorRules -> {[[#1]] -> Apply[[#2]] & Colors}]

Code sample:

Take[a, 2]

{{42., 41., 41., 41., 41., 21., 41., 41., 41., 41., 41., 41., 41., 
  41., 41., 21., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 
  41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 
  41., 41., 41., 41., 41., 41., 11., 11., 11., 11., 11., 11., 11., 
  11., 11., 11., 11., 11., 11., 41., 21., 52., 52., 52., 52., 52., 
  52., 52., 52., 41., 41., 41., 41., 41., 41., 41., 52., 52., 41., 
  52., 52., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 
  21., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 
  41., 52., 52., 95., 95., 42., 21., 95., 90., 90., 41., 95., 95., 
  11., 11., 95., 11., 11., 11., 95., 95., 95., 95., 90., 90., 90., 
  95., 90., 90., 90., 90., 41., 41., 81., 81., 81., 81., 81., 81., 
  81., 81., 81., 81., 81., 71., 71., 71., 41., 41., 41., 21., 41., 
  11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 
  11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 
  90., 90., 41., 21., 41., 41., 41., 41., 41., 41., 95., 95., 41., 
  41., 41., 95., 71., 71.}, {42., 41., 41., 41., 21., 21., 41., 41., 
  41., 41., 41., 41., 41., 41., 41., 41., 21., 21., 21., 21., 21., 
  21., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 
  41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 41., 11., 11., 
  11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 41., 41., 21., 
  52., 52., 52., 52., 52., 52., 41., 41., 41., 41., 41., 41., 41., 
  52., 52., 52., 41., 52., 52., 52., 52., 41., 41., 41., 41., 41., 
  41., 41., 52., 52., 52., 21., 41., 41., 41., 41., 41., 41., 41., 
  41., 41., 41., 41., 41., 52., 52., 52., 52., 42., 42., 22., 90., 
  95., 90., 41., 41., 95., 11., 95., 95., 11., 95., 95., 95., 90., 
  90., 90., 90., 41., 90., 90., 95., 90., 90., 90., 41., 41., 81., 
  81., 81., 81., 81., 81., 81., 81., 81., 81., 81., 41., 71., 41., 
  41., 41., 21., 41., 11., 11., 11., 11., 11., 11., 11., 11., 11., 
  11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 11., 
  11., 11., 11., 90., 90., 90., 90., 21., 21., 41., 41., 41., 41., 
  41., 95., 95., 90., 95., 95., 95., 41., 71., 71.}}

Colors

{{"0.", RGBColor["0.00000000000", "0.00000000000", 
   "0.00000000000"]}, {"11.", 
  RGBColor["0.27843137255", "0.41960784314", 
   "0.62745098039"]}, {"12.", 
  RGBColor["0.81960784314", "0.86666666667", 
   "0.97647058824"]}, {"21.", 
  RGBColor["0.86666666667", "0.78823529412", 
   "0.78823529412"]}, {"22.", 
  RGBColor["0.84705882353", "0.57647058824", 
   "0.50980392157"]}, {"23.", 
  RGBColor["0.92941176471", "0.00000000000", 
   "0.00000000000"]}, {"24.", 
  RGBColor["0.66666666667", "0.00000000000", 
   "0.00000000000"]}, {"31.", 
  RGBColor["0.69803921569", "0.67843137255", 
   "0.63921568628"]}, {"41.", 
  RGBColor["0.40784313726", "0.66666666667", 
   "0.38823529412"]}, {"42.", 
  RGBColor["0.10980392157", "0.38823529412", 
   "0.18823529412"]}, {"43.", 
  RGBColor["0.70980392157", "0.78823529412", 
   "0.55686274510"]}, {"51.", 
  RGBColor["0.64705882353", "0.54901960784", 
   "0.18823529412"]}, {"52.", 
  RGBColor["0.80000000000", "0.72941176471", 
   "0.48627450980"]}, {"71.", 
  RGBColor["0.88627450980", "0.88627450980", 
   "0.75686274510"]}, {"72.", 
  RGBColor["0.78823529412", "0.78823529412", 
   "0.46666666667"]}, {"73.", 
  RGBColor["0.60000000000", "0.75686274510", 
   "0.27843137255"]}, {"74.", 
  RGBColor["0.46666666667", "0.67843137255", 
   "0.57647058824"]}, {"81.", 
  RGBColor["0.85882352941", "0.84705882353", 
   "0.23921568628"]}, {"82.", 
  RGBColor["0.66666666667", "0.43921568628", 
   "0.15686274510"]}, {"90.", 
  RGBColor["0.72941176471", "0.84705882353", 
   "0.91764705882"]}, {"95.", 
  RGBColor["0.43921568628", "0.63921568628", "0.72941176471"]}}

Answer 1

Try with this, as you are importing strings:

Colors = ToExpression@ReadList["nlcd-colors.csv", {"Word", "Word", "Word", "Word"}, 
 WordSeparators -> {"\t", " ", ","}];
rules = ColorRules -> Flatten@{IntegerPart@ToExpression@#[[1]] -> 
   RGBColor[#[[2]], #[[3]], #[[4]]] & /@ Colors}
ArrayPlot[IntegerPart@a, rules]

Edit

Including the style of and suggestions by @kglr:

Colors = ReadList["nlcd-colors.csv", {"Word", {"Word", "Word", "Word"}}, 
WordSeparators -> {"\t", " ", ","}] /. x_String :> ToExpression[x];

rules = ColorRules -> Flatten@{IntegerPart@#[[1]] -> RGBColor @@ #[[2]] & /@ Colors};
ArrayPlot[IntegerPart@a, rules]

Answer 2

Your Colors have Strings inside. For example,

Colors[[2]]

{"11.", RGBColor["0.27843137255", "0.41960784314", "0.62745098039"]}

After replacing strings with expressions

Colors = Colors /. x_String :> ToExpression[x];

and using

ArrayPlot[a, AspectRatio -> 1/10, ColorRules -> (Rule @@@ Colors)]

or

ArrayPlot[a /. (Rule @@@ COlors), AspectRatio -> 1/10]

we get