Vim: How to change the highlight color for search hits and quickfix selection

Look at $VIMRUNTIME/colors/desert.vim. Color mappings are defined there with the hi[ghlight] command. The search highlighting is defined as

hi Search guibg=peru guifg=wheat

for the GUI and

hi Search cterm=NONE ctermfg=grey ctermbg=blue

for terminals.

You can override this setting in your .vimrc using the same command after you select your colorscheme. Type :h hi for help.