diff --git a/lua/colorizer.lua b/lua/colorizer.lua
index f61e480..143b9c3 100644
--- a/lua/colorizer.lua
+++ b/lua/colorizer.lua
@@ -60,6 +60,7 @@
 local buffer_utils = require "colorizer.buffer"
 local clear_hl_cache = buffer_utils.clear_hl_cache
 local rehighlight_buffer = buffer_utils.rehighlight
+local clear_matcher_cache = require("colorizer.matcher").clear_cache
 
 local utils = require "colorizer.utils"
 local merge = utils.merge
@@ -173,6 +174,7 @@ local USER_DEFAULT_OPTIONS = {
   sass = { enable = false, parsers = { css = true } },
   virtualtext = "■",
   always_update = false,
+  custom = nil,
 }
 
 local OPTIONS = { buf = {}, file = {} }
@@ -480,7 +482,11 @@ function colorizer.setup(config)
     all = { file = false, buf = false },
     default_options = user_default_options,
   }
-  BUFFER_OPTIONS, BUFFER_LOCAL = {}, {}
+
+  -- clear autocmds
+  pcall(api.nvim_del_augroup_by_name, AUGROUP_NAME)
+
+  BUFFER_LOCAL = {}
 
   local function COLORIZER_SETUP_HOOK(typ)
     local filetype = vim.bo.filetype
@@ -575,6 +581,19 @@ function colorizer.setup(config)
       require("colorizer").clear_highlight_cache()
     end,
   })
+
+  -- if old buffers, reattach them with new settings
+  local old_buffers = vim.deepcopy(BUFFER_OPTIONS)
+  BUFFER_OPTIONS = {}
+  if old_buffers then
+    clear_matcher_cache()
+    clear_hl_cache()
+    for buf, _ in pairs(old_buffers) do
+      colorizer.detach_from_buffer(buf)
+      colorizer.attach_to_buffer(buf)
+    end
+  end
+
 end
 
 --- Return the currently active buffer options.
diff --git a/lua/colorizer/matcher.lua b/lua/colorizer/matcher.lua
index 1f3eede..f9efd9c 100644
--- a/lua/colorizer/matcher.lua
+++ b/lua/colorizer/matcher.lua
@@ -65,6 +65,11 @@ function matcher.compile(matchers, matchers_trie)
 end
 
 local MATCHER_CACHE = {}
+
+function matcher.clear_cache()
+  MATCHER_CACHE = {}
+end
+
 ---Parse the given options and return a function with enabled parsers.
 --if no parsers enabled then return false
 --Do not try make the function again if it is present in the cache
@@ -112,7 +117,7 @@ function matcher.make(options)
   matchers.max_prefix_length = 0
 
   if enable_names then
-    matchers.color_name_parser = { tailwind = options.tailwind }
+    matchers.color_name_parser = { tailwind = options.tailwind, custom = options.custom }
   end
 
   if enable_sass then
diff --git a/lua/colorizer/parser/names.lua b/lua/colorizer/parser/names.lua
index 6fc7043..55bac5e 100644
--- a/lua/colorizer/parser/names.lua
+++ b/lua/colorizer/parser/names.lua
@@ -57,9 +57,19 @@ function parser.name_parser(line, i, opts)
         end
       end
     end
+
     TAILWIND_ENABLED = opts.tailwind
   end
 
+  if opts and opts.custom then
+    for k, v in pairs(opts.custom) do
+      COLOR_NAME_MINLEN = COLOR_NAME_MINLEN and min(#k, COLOR_NAME_MINLEN) or #k
+      COLOR_NAME_MAXLEN = COLOR_NAME_MAXLEN and max(#k, COLOR_NAME_MAXLEN) or #k
+      COLOR_MAP[k] = string.sub(v, 2)
+      COLOR_TRIE:insert(k)
+    end
+  end
+
   if #line < i + COLOR_NAME_MINLEN - 1 then
     return
   end
diff --git a/lua/colorizer/trie.lua b/lua/colorizer/trie.lua
index a7d9994..64c71dc 100644
--- a/lua/colorizer/trie.lua
+++ b/lua/colorizer/trie.lua
@@ -21,7 +21,7 @@ local ffi = require "ffi"
 ffi.cdef [[
 struct Trie {
 	bool is_leaf;
-	struct Trie* character[62];
+	struct Trie* character[63];
 };
 void *malloc(size_t size);
 void free(void *ptr);
@@ -41,7 +41,7 @@ local function trie_destroy(trie)
   if trie == nil then
     return
   end
-  for i = 0, 61 do
+  for i = 0, 62 do
     local child = trie.character[i]
     if child ~= nil then
       trie_destroy(child)
@@ -52,11 +52,12 @@ end
 
 local total_char = 255
 local INDEX_LOOKUP_TABLE = ffi.new("uint8_t[?]", total_char)
-local CHAR_LOOKUP_TABLE = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-"
+local CHAR_LOOKUP_TABLE = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz-_"
 do
   local b = string.byte
   local extra_char = {
     [b "-"] = true,
+    [b "_"] = true,
   }
   local byte = { ["0"] = b "0", ["9"] = b "9", ["a"] = b "a", ["A"] = b "A", ["z"] = b "z", ["Z"] = b "Z" }
   for i = 0, total_char do
@@ -156,7 +157,7 @@ end
 --- Printing utilities
 
 local function index_to_char(index)
-  if index < 0 or index > 61 then
+  if index < 0 or index > 62 then
     return
   end
   return CHAR_LOOKUP_TABLE:sub(index + 1, index + 1)
@@ -167,7 +168,7 @@ local function trie_as_table(trie)
     return nil
   end
   local children = {}
-  for i = 0, 61 do
+  for i = 0, 62 do
     local child = trie.character[i]
     if child ~= nil then
       local child_table = trie_as_table(child)
diff --git a/lua/colorizer/utils.lua b/lua/colorizer/utils.lua
index ae590cd..29c8046 100644
--- a/lua/colorizer/utils.lua
+++ b/lua/colorizer/utils.lua
@@ -68,7 +68,7 @@ end
 ---@param byte number
 ---@return boolean
 function utils.byte_is_valid_colorchar(byte)
-  return utils.byte_is_alphanumeric(byte) or byte == ("-"):byte()
+  return utils.byte_is_alphanumeric(byte) or byte == ("-"):byte() or byte == ("_"):byte()
 end
 
 ---Count the number of character in a string