The Massachusetts congressional delegation showed its liberal colors and Wyoming was the most conservative state in 1988, according to a survey by the American Conservative Union.

A lawmaker with a rating of 100 percent is one who voted in accordance with the position of the conservative group in all instances. In Massachusetts the average score was just 3.69. In Wyoming, it was 97.3.Based on its selection of 22 key votes in the two chambers, some of which the group gave double weight, the ACU said both the House and Senate voted more conservatively in 1988 than in 1987. The average House rating went from 37 percent to 44 percent, and the Senate average from 40 to 43 percent.

In both chambers, however, the move to the right was made easier by a lack of confrontation over tough budget issues last year, due to the 1987 budget summit, the group said.

Last month, the Americans for Democratic Action, a liberal group, released a similar survey and declared that the Congress had become more liberal.

The differences occur because the two groups base their surveys on different vote lists. However, the surveys do highlight the ideological differences between the parties.

The ACU said four senators and 38 House members, all Republicans, scored 100 percent.

The conservative group in its rating gave double weight to votes on three issues: aid to Nicaraguan Contra rebels, the override of President Reagan's veto ofthe Grove City civil rights extension bill, and a vote on shifting $100 million away from the "Star Wars" missile system.

*****> Utah, Idaho scores

Here are ratings of Utah and Idaho House members released Thursday by the American Conservative Union. A rating of 100 percent indicates that a member agreed with the group in all 22 selected votes in 1988.

IDAHO

Democrat - Stallings, 48.

Republican - Craig, 100.

UTAH

Democrat - Owens, 16.

Republican - Hansen, 100; Nielson, 92.