Access DB for multi-user hosted on server VS. PHP/MySQL

Hi! I have to design a database that will be hosted on an in-house server, where 3-6 user will be simultaneously updating. I would like to know if it can be done with Ms Access or if I'm better off with PHP MySQL... thank you!

Also, using VBA is it possible to change the color of the text in a textbox once it has exceeded 300 caracters?

Q1.
Yes it can be done with Access, but you are still better off with MySQL, its more reliable and scalable.

Q2.

VB Code:

Private Sub TextBox1_Change()
    With Me.TextBox1
        If Len(.Value) > 300 Then
            .BackColor = RGB(255, 0, 0)
        End If
    End With
End Sub

Thanks D!
One last thing, can I change the color of only 300+ caracter??? like the 300 first would be black and change to red for the one after 300...

Its all or nothing I'm afraid. No way to format part of a textbox.