As a premise, it is assumed that the desired wavelength is included within the wavelength range of the white LED.
Below is the typical wavelength distribution of a white LED. It is believed to be applicable in the range of approximately early 400nm to 650nm.
By attaching a band-pass filter to this illumination, it will emit light at specific wavelengths.
For example, if you use the filter indicated by the red arrow below, the light will peak at around 490nm, resulting in blue light.
Although we do not have such equipment, there are general LED illuminations available that can accommodate filter attachments.
Below is a model of white LED illumination from Hayashi Repic Co., the HAD-TW3. (Filters can be attached to the tip of the illumination.)