A new national political party was born today in West Germany that, critics have already predicted, is too colorful to survive but that nonetheless has the mainstream parties fretting more than they usually do during an election year.

Called simply "the Greens," and built on recent successes by environmentalist groups in local West German elections, the new party is actually more than an ecology lobby. It has become a political umbrella for a number of increasingly vigorous protest groups here, both left and right, that hope to draw dissatidfied members from the major political parties.

Representatives of these factions came together this weekend, and the mixed scene of jeans and suit jackets, long hair and thinning scalps, protest buttons and briefcases, looked more like a college reunion than a political convention.

The critical question for convention delegates was what to do about Communists who have sought to join. Many left-leaning Greens wanted to invite them in, but a majority voted against admitting anyone who belonged to another party -- although they left the door open for communist members in some states to join.

Making that decision took half the weekend, and debate and disruption over other founding statutes took up the rest, leaving no time to forge a national party platform -- a task put off to a later date.

Party planner considered it victory enough to have been able to meet in relative peace.

"I was surprised that the right and left sat down and voted together in the small hall," said Karl Kerschgens, a vocational guidance counselor from Darmstadt who regards himself as standing in the political middle.

Since the Greens began in 1978 as a loose coalition of antinuclear groups, they have broadened in aim and appeal. Their four ideological pillars -- protection of the ecology, social equality, grass-roots democracy and nonoviolence -- struck a sympathetic chord among the disenchanted of West Germany's middle class and youth.

So far, the Greens have performed best by taking strong stands on specific issues. They have won in local elections by opposing new highways or by stressing the dangers of chemical plants. Their largest showings have been in university towns or areas near controversial projects.

In October, a Green party captured four seats in Bremen, which brought environemtalists into a West German state legislature for the first time and encourgaed the Green to set up the political machinery for national elections this fall.

Under the West German parliamentary apportionment system, the Green party poses more of a threat that its membership of 10,000 would suggest, particularly for the governing coalition led by the Social Democrats.

The Social Democrats, who received 42.6 percent of the vote in the last election, rule with the Free Democrats, who won 7.9 percent, and together they have 10 more seats than the Christian Democrat-Christian Socialist opposition, which received the most votes of any single party.

A 5 percent minimum is necessary to gain representation in the parliament, and the concern in some political cricles is that the Greens will take votes away from the Free Democrats, thus tipping the balance in favor of the opposition.

Green organizers say they hope to win more than 5 percent and be in a position to form their won coalition with the Social Democrats.

The Green received $2 million in state subsidies last year after drawing more than 3 percent of the national vote in European Parliament elections.

The party lacks a leading personality. Rudi Dutschke, the leader of the West German student movement in 1968, had played a prominent role in environmentalist campaigning before his death last month. Rudolf, Bahro, a Marxist theoretician expelled from East Germany last fall, announced here that he would join, but said he would not play a major role, so as not to contribute to the party's already heavily leftist image.

Another main spokesman for the fledgling party has been Herbert Gruhl, a former Christian Democrat anc current independent member of the Bundestag, who coined the party's slogan: "Neither left nor right but out in front."