No need to use two diferent textView to set the color of a part of the text.

app/src/main/res/layout/fragment_authentication_log_in.xml

@@ -38,30 +38,15 @@
         app:layout_constraintRight_toRightOf="parent"
         app:layout_constraintTop_toBottomOf="@+id/text_username" />
 
-    <LinearLayout
+    <TextView
+        android:id="@+id/text_new_in_rocket_chat"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         android:layout_marginBottom="16dp"
-        android:gravity="center"
-        android:orientation="horizontal"
+        android:text="@string/msg_new_in_rocket_chat"
         app:layout_constraintBottom_toBottomOf="parent"
         app:layout_constraintLeft_toLeftOf="parent"
-        app:layout_constraintRight_toRightOf="parent">
-
-        <TextView
-            android:id="@+id/text_new_in_rocket_chat"
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:text="@string/msg_new_in_rocket_chat" />
-
-        <TextView
-            android:id="@+id/text_sign_up"
-            android:layout_width="wrap_content"
-            android:layout_height="wrap_content"
-            android:layout_marginStart="5dp"
-            android:text="@string/title_sign_up"
-            android:textColor="@color/colorAccent" />
-    </LinearLayout>
+        app:layout_constraintRight_toRightOf="parent" />
 
     <Button
         android:id="@+id/button_log_in"

app/src/main/res/values-pt-rBR/strings.xml

@@ -15,7 +15,7 @@
     <string name="msg_password">senha</string>
     <string name="msg_name_and_surname">nome e sobrenome</string>
     <string name="msg_email">email</string>
-    <string name="msg_new_in_rocket_chat">Novo no Rocket Chat?</string>
+    <string name="msg_new_in_rocket_chat">Novo no Rocket Chat? <font color='#FF1976D2'>Inscreva-se</font></string>
     <string name="msg_new_user_agreement">Ao proceder você concorda com nossos\n<font color='#FF1976D2'>Termos de Serviço</font> e <font color='#FF1976D2'>Política de Privacidade</font></string>
     <string name="msg_2fa_code">Código 2FA</string>
 

app/src/main/res/values/strings.xml

@@ -16,7 +16,7 @@
     <string name="msg_password">password</string>
     <string name="msg_name_and_surname">name and surname</string>
     <string name="msg_email">email</string>
-    <string name="msg_new_in_rocket_chat">New in Rocket Chat?</string>
+    <string name="msg_new_in_rocket_chat">New in Rocket Chat? <font color='#FF1976D2'>Sign up</font></string>
     <string name="msg_new_user_agreement">By proceeding you are agreeing to our\n<font color='#FF1976D2'>Terms of Service</font> and <font color='#FF1976D2'>Privacy Policy</font></string>
     <string name="msg_2fa_code">2FA Code</string>