In a large bowl, beat butter and sugars with an electric mixer on medium speed until light and fluffy 2-3 minutes. Mix in milk and vanilla. Stir in flour and salt and mix on low speed until incorporated. Gently fold in M&M's.

Chill in the refrigerator for 15-30 minutes. Then roll into small balls.

Place rolled balls on a wax paper lined baking sheet and place in the freezer for at least 15 minutes or up to an hour.

Melt candy coating following instructions on the package. If using chocolate chips, melt in the microwave 30 seconds at a time until smooth, stirring in between each 30 seconds. Remove a couple of balls from the freezer at a time and dip in melted chocolate using a fork or a dipping tool. Remove from chocolate and holding it above the chocolate let excess chocolate drip down. Place on wax paper. Continue until all truffles are covered in chocolate.

Optional: If you want to top with sprinkles do that right after dipping truffles in chocolate. If you'd like to drizzle on blue and pink candy melts let chocolate set (put in fridge or freezer) then drizzle on the candy melts. (You can use a ziplock bag with the corner snipped to use as a piping bag.)

Refrigerate in an airtight container for up to 3 days.