diff --git a/httpie/output/formatters/colors.py b/httpie/output/formatters/colors.py
index 52f5a22a..cf4c8e26 100644
--- a/httpie/output/formatters/colors.py
+++ b/httpie/output/formatters/colors.py
@@ -1,5 +1,6 @@
 from __future__ import absolute_import
 import json
+from typing import Type
 
 import pygments.lexer
 import pygments.token
@@ -13,6 +14,7 @@ from pygments.lexers.text import HttpLexer as PygmentsHttpLexer
 from pygments.util import ClassNotFound
 
 from httpie.compat import is_windows
+from httpie.context import Environment
 from httpie.plugins import FormatterPlugin
 
 
@@ -40,8 +42,13 @@ class ColorFormatter(FormatterPlugin):
     """
     group_name = 'colors'
 
-    def __init__(self, env, explicit_json=False,
-                 color_scheme=DEFAULT_STYLE, **kwargs):
+    def __init__(
+        self,
+        env: Environment,
+        explicit_json=False,
+        color_scheme=DEFAULT_STYLE,
+        **kwargs
+    ):
         super().__init__(**kwargs)
 
         if not env.colors:
@@ -63,14 +70,14 @@ class ColorFormatter(FormatterPlugin):
         self.formatter = formatter
         self.http_lexer = http_lexer
 
-    def format_headers(self, headers):
+    def format_headers(self, headers: str) -> str:
         return pygments.highlight(
             code=headers,
             lexer=self.http_lexer,
             formatter=self.formatter,
         ).strip()
 
-    def format_body(self, body, mime):
+    def format_body(self, body: str, mime: str) -> str:
         lexer = self.get_lexer_for_body(mime, body)
         if lexer:
             body = pygments.highlight(
@@ -80,21 +87,29 @@ class ColorFormatter(FormatterPlugin):
             )
         return body.strip()
 
-    def get_lexer_for_body(self, mime, body):
+    def get_lexer_for_body(
+        self, mime: str,
+        body: str
+    ) -> Type[pygments.lexer.Lexer]:
         return get_lexer(
             mime=mime,
             explicit_json=self.explicit_json,
             body=body,
         )
 
-    def get_style_class(self, color_scheme):
+    @staticmethod
+    def get_style_class(color_scheme: str) -> Type[pygments.style.Style]:
         try:
             return pygments.styles.get_style_by_name(color_scheme)
         except ClassNotFound:
             return Solarized256Style
 
 
-def get_lexer(mime, explicit_json=False, body=''):
+def get_lexer(
+    mime: str,
+    explicit_json=False,
+    body=''
+) -> Type[pygments.lexer.Lexer]:
 
     # Build candidate mime type and lexer names.
     mime_types, lexer_names = [mime], []
diff --git a/httpie/output/formatters/headers.py b/httpie/output/formatters/headers.py
index 146dea3c..486f09f6 100644
--- a/httpie/output/formatters/headers.py
+++ b/httpie/output/formatters/headers.py
@@ -3,7 +3,7 @@ from httpie.plugins import FormatterPlugin
 
 class HeadersFormatter(FormatterPlugin):
 
-    def format_headers(self, headers):
+    def format_headers(self, headers: str) -> str:
         """
         Sorts headers by name while retaining relative
         order of multiple headers with the same name.
diff --git a/httpie/output/formatters/json.py b/httpie/output/formatters/json.py
index 9af5db1a..d2eb52d3 100644
--- a/httpie/output/formatters/json.py
+++ b/httpie/output/formatters/json.py
@@ -9,7 +9,7 @@ DEFAULT_INDENT = 4
 
 class JSONFormatter(FormatterPlugin):
 
-    def format_body(self, body, mime):
+    def format_body(self, body: str, mime: str) -> str:
         maybe_json = [
             'json',
             'javascript',
diff --git a/httpie/output/processing.py b/httpie/output/processing.py
index 98270985..9bee2621 100644
--- a/httpie/output/processing.py
+++ b/httpie/output/processing.py
@@ -40,12 +40,12 @@ class Formatting:
                 if p.enabled:
                     self.enabled_plugins.append(p)
 
-    def format_headers(self, headers):
+    def format_headers(self, headers: str) -> str:
         for p in self.enabled_plugins:
             headers = p.format_headers(headers)
         return headers
 
-    def format_body(self, content, mime):
+    def format_body(self, content: str, mime: str) -> str:
         if is_valid_mime(mime):
             for p in self.enabled_plugins:
                 content = p.format_body(content, mime)