Voting rights: what class of votes could vote for which house of congress?

The 15th Amendment states: "The right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of race, color, or previous condition of servitude."

The bill passed the House in a 286-126 vote. Only 51 percent of Democrats voted in favor of the bill, or 119 of their 235 members, compared to 84 percent of Republicans, or 167 of their 199 members.