  We report continuous loading of $^{\textrm{87}}$Rb atoms in a magneto-optical
trap (MOT) at narrow linewidth, 420 nm 5S$_{1/2}$, F$=2\rightarrow$ 6P$_{3/2}$,
F$=3$ blue transition (blue MOT). Continuous loading of the blue MOT is
achieved by superimposing the blue laser beam, inside a hollow core of infrared
laser beam driving the broad 5S$_{1/2}$, F$=2\rightarrow$ 5P$_{3/2}$, F$=3$
transition at 780 nm. We typically load $\sim10^{8}$ atoms in the blue MOT in
2.5 seconds. We characterize the continuous loading of blue MOT with various
parameters such as magnetic field gradient, detuning, power and diameter of
blue MOT beam and diameter of the hollow core (spot) inside the IR MOT beam. We
observe that the blue laser beam should overfill the spot of the IR laser beam.
This is because the blue laser cools the atoms to a lower temperature even in
the presence of the broad IR laser i.e. in the overlapped region and hence
helps in loading. We also present the theoretical framework for cooling atoms
in the presence of simultaneously two transitions to support the experimental
result. This method of continuous loading of the blue MOT can be useful to
produce a continuous atomic beam of cold Rb atoms.
