How to wire two switches to control bathroom fan/light combo (only two 12/2 cables in receptacle)?
Each of these cables is a switch loop. In theory, the taped white (red or blue) is the always-hot wire and the black wire is the switched-hot. However, it could be the reverse. There are two easy ways to tell:

Open up the fan and light and see which wire is connected to another black (= always hot) and which is connected to the fan or light (= switched hot)
With all the wires carefully separated, turn the breaker back on and see which wires show hot with a non-contact tester.

Once you know which wires are always hot and which wires are switched hot:

For a standard &quot;both screws are the same, nothing fancy&quot; light switch, connect one insulated wire to one screw, the other insulated wire to the other screw, bare ground to the green screw and done.
For the timer:

Connect (wire nut) bare ground to green
Connect (wire nut) always-hot wire to black
Connect (wire nut) switched-hot wire to red