A Facebook group called Rainbow Trail Australia is inspiring colourful artworks across the nation to "spread some joy during these testing times".

The group was created on March 21 and has gained more than 120,000 members within a fortnight.

Members are encouraged to draw rainbows on streets and footpaths, or to produce other colourful creations, to brighten people's day in the face of the coronavirus pandemic and associated social-distancing rules.

In South Australia, Murray Bridge High students added their own artistic efforts to the trail this week, using handprints to paint a multi-hued tree which has been hung at the school's main entrance.

Staff member Nicolene Timmo said her equal-opportunity education students had jumped at the idea of joining in.

"We thought, 'what better way to give our kids some hands-on activities while they can?'" she said.

"We were on Facebook and saw the Rainbow Trail was all over, just to brighten people up ... why not do something similar?"

They had originally planned to do some chalk drawings like the ones most group members have completed on footpaths, roads and walls, but wound up inviting any willing students to leave their imprint on the tree during a lunch break.

Other Murraylands artists have drawn rainbows, love hearts, smiley faces or characters on footpaths and driveways, coloured in pavers or bricks individually or stuck drawings in windows.