Change DebugLevel color to gray

text_formatter.go

diff --git a/text_formatter.go b/text_formatter.go
index 4e51734..4f50a60 100644
--- a/text_formatter.go
+++ b/text_formatter.go
@@ -15,6 +15,7 @@
 	green   = 32
 	yellow  = 33
 	blue    = 34
+	gray    = 37
 )
 
 var (
@@ -75,6 +76,8 @@
 func printColored(b *bytes.Buffer, entry *Entry, keys []string) {
 	var levelColor int
 	switch entry.Level {
+	case DebugLevel:
+		levelColor = gray
 	case WarnLevel:
 		levelColor = yellow
 	case ErrorLevel, FatalLevel, PanicLevel: