By Andrew Black
Political reporter, BBC Scotland news website
As a big man once sang, it's not easy being green - but the Scottish Green Party , in its short history, has become something of a trailblazer for similar parties across the world.
Shiona Baird and Robin Harper launching the party's manifesto in 2007
While green campaigners have been prominent for many years, the recent explosion of environmental issues to the top of the agenda has seen mainstream political parties getting in on the act like never before.
The decision to introduce PR voting in the first Scottish Parliament elections for 300 years was designed to produce a "rainbow parliament", where smaller parties had a fairer chance of winning seats.
And so it was the case that, in 1999, one of Scottish politics' most intriguing characters, Robin Harper, was duly returned as MSP for the Lothian regional list, as the Green Party's first UK parliamentarian.
With his fedora hat, multi-coloured scarf and eccentric style, the comparisons between Mr Harper and Doctor Who (of the Tom Baker era) were almost instant.
Ecology to Greens
The former teacher was quickly dubbed one of the "three amigos", along with Socialist Tommy Sheridan and firebrand independent Dennis Canavan, after they resisted attempts to move them to the back of the Holyrood chamber - even threatening a sit-in.
Over the next four years, Mr Harper single-handedly pressed the Scottish government on environmental issues, demanding the destruction of GM crops and taking part in anti-nuclear demonstrations.
In the grand scheme of politics, the party did not have to wait too long for electoral success - the Scottish Greens formed in 1990, moving away from it's UK party, in line with its de-centralisation policy.
The movement had its beginnings in the Ecology Party, founded in 1973, before becoming the Green Party a decade later.
The Scottish Green Party won seven seats at the Holyrood election in 2003
Fast forward to the 2003 Scottish Parliament election and the Greens saw an opportunity to up their representation by homing in on the second, regional list vote, and voters supportive to the party cause.
There were many reasons which led to the historic return of seven Green MSPs that year across Scotland - including a degree of voter disillusionment with Labour and the SNP - and the fact it was seen as "fashionable" at the time to vote Green.
The Scottish Greens would probably argue it was down to their policies and the lack of their opponents' environmental credentials - whatever the reason, the party had become a serious player in Scottish politics.
Over the next four years, the party took on issues such as opposing ID cards, dawn raids on families of failed asylum seekers and called for reforms of the planning system.
Then came the 2007 election. The smaller parties knew it would be tough, but the Greens set out a goal to return at least 10 MSPs, saying support for their party was "no longer a protest vote, but a progress vote".
The party manifesto was wide-ranging and controversially included a pledge on integrating state-funded religious schools into nondenominational education, with the party moving to deny it was a move to "abolish" Catholic education.
But the polls saw an extreme squeeze in the fight for votes between Labour and the SNP and, although the Greens avoided the electoral wipeout - which killed off the other small parties - by winning council seats for the first time and returning two MSPs.
One was Robin Harper, the other was Patrick Harvie, who had built up a reputation as a skilled debater and politician.
Rather than wallow in defeat, the new, leaner Green parliamentary group threw itself into coalition talks with the SNP, after it emerged as the largest party by one seat.
In theory it was a great match - both parties were pro-independence and anti-nuclear - but the negotiations came to nothing, amid disagreement over the Nationalist's transport policy.
In the end, the two Green MSPs agreed to vote for SNP leader Alex Salmond as first minister and support his appointments, while in return agreed to an early introduction of the historic Climate Change Bill and nomination of a Green MSP to chair a Holyrood committee.
Later that year, Mr Harvie told his party's conference the Greens needed to up their game in order to regain lost ground, partly by going after donations beyond its core supporters - something the party had shunned in the past.
He told delegates at the time: "Very often I hear Greens say things with the best of intentions like 'our single greatest asset is that we're right' as though that will simply result in eventually everybody realising we're right. Being right isn't enough."
"If we want to regain the ground that we've lost and more besides, there are some things that we need to do, some of which don't come naturally to us, some of which won't feel comfortable to us."
Patrick Harvie told his party it needed to up its game
The party began on the road to recovery, pushing its green agenda, but its two MSPs began to feel they were increasingly being taken for granted by the minority SNP government.
In January 2009, Messers Harper and Harvie withdrew their support for the Scottish budget shortly before a crunch vote in a row over support for the Greens' home insulation scheme policy.
The budget fell and was later passed on the second attempt, but the defeat served as a timely reminder to the SNP that, despite their depleted numbers, the Greens could still be a force to be reckoned with.
The Greens came to the fore more recently, after the Scottish Parliament passed a motion from the party to reject plans for a coal-fired power station at Hunterston in North Ayrshire.
It would be the UK's first carbon capture plant but critics said the technology remained unproven and, while ministers considering the application could ignore the vote, MSPs still chose to send a message on the plans.
There was also personal success for Mr Harvie, whose backbench bill to tackle hate crimes against gay or disabled people was passed by parliament.
Mr Harper had also announced his intention to step down as an MSP, after 10 years of elected life.
He called on the party, which had elected male and female co-conveners in line with its equal status policy, to opt for a single leader - opening the door for the ambitious Mr Harvie to take the reins as the only obvious successor.
Mr Harper may not have had a reputation as the most skilled Holyrood debater or political operator, but fact that he served alongside 15 Scottish party leaders - outlasting 11 of them - was testament to his popularity in a Scottish Parliament which had seen massive change since 1999.
But as one era ends, another one begins. The Green Party - both north and south of the border, is hoping to land its first MP in the forthcoming election.