synchronize unread-badge-color with desktop and android (#1407)

DcCore/DcCore/Helper/DcColors.swift

@@ -18,6 +18,7 @@ public struct DcColors {
     public static let sharedChatCellBackgroundColor = UIColor.themeColor(light: white, dark: actionCellBackgroundDark)
     public static let chatBackgroundColor = UIColor.themeColor(light: .white, dark: .black)
     public static let checkmarkGreen = UIColor.themeColor(light: UIColor.rgb(red: 112, green: 177, blue: 92))
+    public static let unreadBadge = UIColor(hexString: "3792fc")
     public static let defaultTextColor = UIColor.themeColor(light: .darkText, dark: .white)
     public static let grayTextColor = UIColor.themeColor(light: .darkGray, dark: .lightGray)
     public static let grayDateColor = UIColor.themeColor(lightHex: "999999", darkHex: "bbbbbb") // slight variations of lightGray (#aaaaaa)

deltachat-ios/View/ContactCell.swift

@@ -251,7 +251,7 @@ class ContactCell: UITableViewCell {
             pinnedIndicator.isHidden = !(visibility == DC_CHAT_VISIBILITY_PINNED)
             unreadMessageCounter.setCount(unreadCount)
             unreadMessageCounter.isHidden = isContactRequest
-            unreadMessageCounter.backgroundColor = isMuted ? .gray : .red
+            unreadMessageCounter.backgroundColor = isMuted ? .gray : DcColors.unreadBadge
             deliveryStatusIndicator.isHidden = true
             archivedIndicator.isHidden = true
         } else {