It is known and intentional that the new client no longer offers support for BBCode. It was kept for channel descriptions for legacy compatibility or something, but IMHO this should also be removed in the future to prevent confusion.
The client does however support Markdown as many other popular chat applications. You can see a list of the supported markdown syntax here.
Color support in markdown was discussed in the past already and will hopefully be implemented in the standard MD way through HTML tags.
