Here in the span of $5$ minutes there is $2$ minute of $"no"$ waiting time and $3$ minute of waiting time that depends on the arrival, it could take any value from $0-3$ minutes.
So I am assuming that starting $3$ minutes its RED and last $2$ min its GREEN.
$\therefore $ the function of waiting time is $\color{Blue }{3-x}$ $\{$ if a person arrive at time 0 it will wait for 3 minutes and soon and so forth.$\}$
Since its uniformly distributed expected waiting time will be :
$\Rightarrow $ $\Large \frac{1}{5-0}\int_{0}^{3}(3-x) \ dx$
$\Rightarrow $$\Large \frac{1}{5}[9-\frac{9}{2}]$
$\Rightarrow $$\Large \frac{9}{10}=\color{Red}{0.9}$