Tips for remembering the colors: नीली is blue like the Nile, पीली is yellow like, um... pee :)
For masculine objects, you can use "nela" and "pela". Kitaabein (books) are feminine so "neeli" and "peeli" are used.
My wordbank had "&" and "and" as an option and I used the former and it was marked as incorrect, but the ampersand does mean "and".
क्या कुछ किताबें नीली और अन्य किताबें पीली हैं, या हर किताब नीली और पीली दोनों है? (Please feel free to correct my hindi sentence)
Are some of the books blue and the others yellow, or are each of the books both blue and yellow?