Fun fact, China literally advertise its red theme as "blood of passed heros". So communism do get its red from blood.

Google translated source (from an official .gov.cn site): https://www-mod-gov-cn.translate.goog/gfbw/jmsd/4851751.html?_x_tr_sch=http&_x_tr_sl=auto&_x_tr_tl=en&_x_tr_hl=en-US&_x_tr_pto=wapp

Quote in Chinese:

为什么说共和国是红色的？对于这个问题，每个人都可能问了数百遍，老师和家长们也早已给出了答案：那是因为共和国是用英烈的鲜血换来的，共和国的血脉里有英烈们的红色基因、红色传统。

Google tranlate:

Why is the Republic said to be red? Everyone may have asked this question hundreds of times, and teachers and parents have already given the answer: That is because the Republic was bought with the blood of heroes, and the blood of the Republic contains the red genes and red blood of the heroes. Tradition.