Yellow, green, and white can all appear as odd looking colors in the paint pot, but when put to canvas and viewed as a whole, the painting looks fantastic! Yellow in a painting can appear green or sometimes whiteish in the paint pot. As you can see, though, once the entire painting is completed, the paint colors work perfectly. White can appear as pink or blue at times, depending on these factors and slight tints that are added to the paint at times.
When viewing the paint in the pot in isolation, without any surrounding colors on a blank white canvas, this may influence perception. Additionally, variations may arise due to lighting conditions, as the paint pot is often viewed indoors under artificial lighting, whereas the final artwork may be observed under natural or different artificial lighting setups. The number of coats of paint and the skill with which the artist has applied that paint all make a difference. Skills like blending and texturing will certainly make a more vibrant painting.
While these variations may initially raise questions, it is important to recognize that the purpose of paint by numbers is to create a visually pleasing piece of art, regardless of the perception of minor deviations in color appearance.