Yes it depends on wave lenght it is inversely proptional to it

u(refrac index ) = c/v c= speed in vac v=speed in med And v=fl f frequency l wave length So we get U1 /U2 = l2/l1

Yes it depends on wave length it is inversely proportional to it. Let $u$ denote the refractive index, then:

$$u = c/v $$ where $c$ in the speed of light in vacuum and $v$ is the speed in a medium. And: $$v=fl$$ where $f$ denotes the frequency and $l$ the wavelength. So we get: $$ \frac{U_1}{U_2} = \frac{l_2}{l_1}$$