How did Newton use creativity and logic in his approach to investigate light

Newtons approach was creative because he thought of the new idea passing a single color of light through a prism. His approach was also logical. He reasoned that comparing white light and a single color of light would allow him to compare the two hypothesis.

Isaac Newton was creative in his use of prisms to show how white light is actually made up of multiple colors. He used logic in the way he presented his arguments rhetorically in order to convince readers of the correctness of his conclusions.

Newton was not the first to experiment with passing light through prisms to determine how light works. French philosopher Rene Descartes had done prism experiments of his own. But Descartes had thought that passing through a prism actually modified the light in order to produce the color spectrum. Newton correctly understood that when light refracted through the prism, it revealed the range of colors that were naturally in the light. He then used a second prism, blocking all but one color, to show that a single color passing through a prism was not modified in color. He also showed--by positioning the second prism differently--how the multiple colors of light could be recombined into white light again.

Newton's 1672 paper on light refracting through prisms established his reputation as a scientist. He continued to study light throughout his scientific career, publishing a larger work in 1704 on Opticks (as they spelled "optics" then).