You have to choose at least 1 color.
105.4. If a player is asked to choose a color, they must choose one of the five colors. “Multicolored” is not a color. Neither is “colorless.”
Prismatic Lace instructs you to choose a color or combination of colors. If you were allowed to choose zero colors, the instruction would be worded such that the zero choice would be obviously allowed, for example by containing the phrase "any number of...". There is also the wording that a player may make a choice, in which case you could avoid choosing at all, rather than choosing zero colors. However, there is no mechanical difference between these approaches, the result would be the same.
Also, just in case, don't get hung up on the potential difference between "a color" and "the color" - unless a term or phrase is defined in the Comprehensive Rules, apply the normal rules of English to it.