package/vim/vim.mk

define VIM_REMOVE_DOCS
        find $(TARGET_DIR)/usr/share/vim -type f -name "*.txt" -delete
endef

This removes file rgb.txt which is used by vim in syntax coloring.
Then, when vim tries to color it's output, you could see something in the sort of:

Error detected while processing /usr/share/vim/vim80/syntax/syncolor.vim: 
line 46: 
E254: Cannot allocate color SlateBlue 
Press ENTER or type command to continue